Tuesday, November 16, 2010
The one and only one for me you are,
You are my shining star,
You are the moon at night,
You are the shining sun at day.
Even the moon has spots on her face,
But your face surely has d ultimate grace.
Your eye reflects an adoring gaze,
And your tenderness gives me strength to solves any hardest maze.
Any galaxy doesn't have such a star as you are,
From ur beauty they are so far.
You shine brighter than bright,
Your beauty on the darkest night.
Even a red beautiful rose before u is shy,
Looking at you makes my heart fly.
In my heart u will stay ever,
And i shall promise to leave u never.
I will guide to outta each night,
With you each battle i shall fight.
I only want u and nothing more,
So please accept my heart waiting at its core.
I shall always stand by you forevermore,
Giving u strength,
Giving u courage.
In my eyes i only will see you,
And always will be with you.
Monday, November 15, 2010
OverviewA ballistic body is a body which is free to move, behave, and be modified in appearance, contour, or texture by ambient conditions, substances, or forces, as by the pressure of gases in a gun, by rifling in a barrel, by gravity, by temperature, or by air particles.
Firearm ballistics information can also be used in forensic science. Separately from ballistics information, firearm and tool mark examinations involve analyzing firearm, ammunition, and tool mark evidence in order to establish whether a certain firearm or tool was used in the commission of a crime.
Ballistics is sometimes subdivided into:
* Internal ballistics, the study of the processes originally accelerating the projectile, for example the passage of a bullet through the barrel of a rifle;
* Transition ballistics, (sometimes called intermediate ballistics) the study of the projectile's behavior when it leaves the barrel and the pressure behind the projectile is equalized.
* External ballistics, the study of the passage of the projectile through space or the air; and
* Terminal ballistics, the study of the interaction of a projectile with its target, whether that be flesh (for a hunting bullet), steel (for an anti-tank round), or even furnace slag (for an industrial slag disruptor).
A ballistic missile is a missile designed to operate in accordance with the laws of ballistics.
The term ballistics is also sometimes used to refer to acceleration curves applied to the motion of a computer mouse.
In the field of forensic science, forensic ballistics is the science of analyzing firearm usage in crimes. It involves analysis of bullets and bullet impacts to determine the type.
Rifling, which first made an appearance in the 15th century, is the process of making grooves in gun barrels that imparts a spin to the projectile for increased accuracy and range. Bullets fired from rifled weapons acquire a distinct signature of grooves, scratches, and indentations which are somewhat unique to the weapon used.
The first firearms evidence identification can be traced back to England in 1835 when the unique markings on a bullet taken from a victim were matched with a bullet mold belonging to the suspect. When confronted with the damning evidence, the suspect confessed to the crime.
The first court case involving firearms evidence took place in 1902 when a specific gun was proven to be the murder weapon. The expert in the case, Oliver Wendell Holmes, had read about firearm identification, and had a gunsmith test-fire the alleged murder weapon into a wad of cotton wool. A magnifying glass was used to match the bullet from the victim with the test bullet.
Calvin Goddard, physician and ex-army officer, acquired data from all known gun manufacturers in order to develop a comprehensive database. With his partner, Charles Waite, he catalogued the results of test-firings from every type of handgun made by 12 manufacturers. Waite also invented the comparison microscope. With this instrument, two bullets could be laid adjacent to one another for comparative examination.
In 1925 Goddard wrote an article for the Army Ordnance titled "Forensic Ballistics" in which he described the use of the comparison microscope regarding firearms investigations. He is generally credited with the conception of the term "forensic ballistics", though he later admitted it to be an inadequate name for the science.
In 1929 the St. Valentine's Day Massacre led to the opening of the first independent scientific crime detection laboratory in the United States.
The Manufacture of Smokeless Powders and their
Smokeless powders are a class of propellants that were developed in the late 19th century to replace black powder. The term smokeless refers to the minimal residue left in the gun barrel following the use of smokeless powder. In forensic analysis, smokeless powders are often encountered as organic gunshot residue or as the explosive charge in improvised explosive devices.
All smokeless powders can be placed into one of three different classes according to the chemical composition of their primary energetic ingredients. A single-base powder contains nitrocellulose, whereas a double-base powder contains nitrocellulose and nitroglycerine. The energetic ingredients in triple-base powders are nitrocellulose, nitroglycerine, and nitroguanidine, but because triple-base powders are primarily used in large caliber munitions, they are difficult to obtain on the open market.
Composition and Manufacturing
The major classes of compounds in smokeless propellants include energetics, stabilizers, plasticizers, flash suppressants, deterrents, opacifiers, and dyes (Bender 1998; Radford Army Ammunition Plant 1987).
- Energetics facilitate the explosion. The base charge is nitrocellulose, a polymer that gives body to the powder and allows extrudability. The addition of nitroglycerine softens the propellant, raises the energy content, and reduces hygroscopicity. Adding nitroguanidine reduces flame temperature, embrittles the mixture at high concentration, and improves energy-flame temperature relationship.
- Stabilizers prevent the nitrocellulose and nitroglycerine from decomposing by neutralizing nitric and nitrous acids that are produced during decomposition. If the acids are not neutralized, they can catalyze further decomposition. Some of the more common stabilizers used to extend the safe life of the energetics are diphenylamine, methyl centralite, and ethyl centralite.
- Plasticizers reduce the need for volatile solvents necessary to colloid nitrocellulose, soften the propellant, and reduce hygroscopicity. Examples of plasticizers include nitroglycerine, dibutyl phthalate, dinitrotoluene, ethyl centralite, and triacetin.
- Flash suppressants interrupt free-radical chain reaction in muzzle gases and work against secondary flash. They are typically alkali or alkaline earth salts that either are contained in the formulation of the propellant or exist as separate granules.
- Deterrents coat the exterior of the propellant granules to reduce the initial burning rate on the surface as well as to reduce initial flame temperature and ignitability. The coating also broadens the pressure peak and increases efficiency. Deterrents may be a penetrating type such as Herkoteâ, dibutyl phthalate, dinitrotoluene, ethyl centralite, methyl centralite, or dioctyl phthalate; or an inhibitor type such as Vinsolâ resin.
- Opacifiers enhance reproducibility primarily in large grains and keep radiant heat from penetrating the surface. They may also enhance the burning rate. The most common opacifier is carbon black.
- Dyes are added mainly for identification purposes.
- Other ingredients may be one of the following:
- A graphite glaze used to coat the powder to improve flow and packing density as well as to reduce static sensitivity and increase conductivity
- Bore erosion coatings applied as a glaze to reduce heat transfer to the barrel, but uncommon in small-arms propellants
- Ignition aid coatings that are most commonly used in ball powders to improve surface oxygen balance
Morphology also lends clues to whether a powder is single- or double-base (Bender 1998). Most tube and cylindrical powders are single-base, with the exception of the Hercules Reloaderâseries. Disc powders, ball powders, and aggregates are double-base, with the exceptions being the PB and SR series powders manufactured by IMR Powder Company of Plattsburg, New York.
Except for ball powder, smokeless powder is manufactured by one of two general methods, differing in whether organic solvents are used in the process (Meyer 1987; Radford Army Ammunition Plant 1987). A single-base powder typically incorporates the use of organic solvents. Nitrocellulose of high- and low-nitrogen content are combined with volatile organic solvents, desired additives are blended with them, and the resulting mixture is shaped by extrusion and cut into specified lengths. The granules are screened to ensure consistency, and the solvents are removed. Various coatings, such as deterrents and graphite, are applied to the surface of the granules. The powder is dried and screened again, then blended to achieve homogeneity.
The manufacture of double-base powders requires the addition of nitroglycerine to the nitrocellulose. Two methods can be used. One method uses organic solvents, the other uses water. The organic solvent method mixes nitrocellulose and nitroglycerine with solvents and any desired additives to form a doughy mixture (Meyer 1987; National Research Council 1998; Radford Army Ammunition Plant 1987). The mixture is then pressed into blocks that can be fed into the extrusion press and cutting machine. The resulting granules are screened prior to solvent removal and the application of various coatings. The powder is dried, screened again, then blended to achieve homogeneity. The water method adds the nitroglycerine to a nitrocellulose water suspension to form a paste (Meyer 1987; Radford Army Ammunition Plant 1987). The water is removed by evaporation on hot rollers, then the dried powder is shaped by extrusion and cutting.
Triple-base powders use a solvent-based process similar to the double-base powder process (Meyer 1987; Radford Army Ammunition Plant 1987). Nitrocellulose and nitroglycerine are premixed with additives prior to the addition of a nitroguanidine solvent mixture. The nitroguanidine is incorporated into the overall mass without dissolving in the other materials. The final mixture is then extruded, cut, and dried.
The manufacture of smokeless ball powder requires a more specialized procedure (National Research Council 1998). Nitrocellulose, stabilizers, and solvents are blended into a dough, then extruded through a pelletizing plate and formed into spheres. The solvent is removed from the granules, and nitroglycerine is impregnated into the granules. The spheres are then coated with deterrents and flattened with rollers. Finally, an additional coating with graphite and flash suppressants is applied, and the batch is mixed to ensure homogeneity.
In the manufacturing process, smokeless powders are recycled and reworked (National Research Council 1998). When a powder within a batch is found to be unsatisfactory, it is removed and returned to the process for use in another lot. Manufacturers save money by recycling returns by distributors or the return of surplus or obsolete military powders. Hence, reworking and recycling the material assures good quality control of the final product, reduces costs by reusing materials, and reduces pollution by avoiding destruction by burning.
The production of smokeless powders is big business in the United States, where approximately 10 million pounds of commercial smokeless powders are produced each year. Most of the powder is sold to the original-equipment manufacturers to be used for manufacturing ammunition. A large amount is sold to domestic and foreign militaries (National Research Council 1998). The rest is sold in individual canisters (ranging from ½-pound cans to 12- or 20-pound kegs) to gun stores or hunting and shooting clubs for hunters and target shooters who prefer to hand load their own ammunition.
There are several ways smokeless powders are distributed within the United States (National Research Council 1998). Some manufacturers, foreign or domestic, produce, package, and sell their own powders commercially. They may also sell in bulk to resellers and to original-equipment manufacturers that repackage and sell it under their own labels. The powder manufacturers and repackagers may disburse large quantities of canister powders to distributors who later sell to smaller distributors and wholesalers, who in turn, supply cans to dealers, gun shops, shooting clubs, and other retailers. At this point, consumers can purchase a 1-pound canister of powder for approximately $15 to $20 from a retailer, though the cost per pound can be cheaper if bought by the keg or acquired through a gun club (National Research Council 1998).
Manufacturers who produce smokeless powders for the U.S. military can distribute it either by selling the powder directly to the military or by selling them the preloaded ammunition. Powders can also be shipped to U.S. military subcontractors, foreign governments, or foreign loading companies for loading into military ammunition (National Research Council 1998).
Improvised Explosive Devices
An explosion is the result of energy-releasing reactions, generally accompanied by the creation of heat and gases (a notable exception is thermites). A distinguishing characteristic of an explosion is the rate at which the reaction proceeds. There are low-order and high-order explosives, based on the speed at which the explosives decompose. In low-order explosives, the process of decomposition, called the speed of deflagration or burning, produces heat, light, and a subsonic pressure wave. (The reaction speed of the deflagrating material is less than the speed of sound.) In high-order explosives, decomposition occurs at the speed of detonation, creating a supersonic shock wave that causes a virtually instantaneous buildup of heat and gases. Table 1 shows some differences in low-order and high-order explosives (Bureau of Alcohol, Tobacco and Firearms 1994; National Research Council 1998; Saferstein 1998).
High Explosive Detonation
|Initiation Method|| |
Shock (from detonator or primary explosive)
|Reaction Time|| |
|Pressure at Reaction Front|| |
|Velocity of Reaction Front|| |
|Temperature in Reaction Zone|| |
The safest and most powerful low-order explosive is smokeless powder. These powders decompose at rates up to 1,000 meters per second and produce a propelling action that makes them suitable for use in ammunition. However, the slower burning rate of smokeless powder should not be underestimated. The explosive power of smokeless powder is extremely dangerous when confined to a small container. In addition, certain smokeless powders with a high-nitroglycerine concentration can be induced to detonate. On the other hand, high-order explosives do not need containment to demonstrate their explosive effects (Saferstein 1998). These materials detonate at rates from 1,000 to 8,500 meters per second, producing a shock wave with an outward rush of gases at supersonic speeds. This effect proves to be more destructive than the fragmented debris.
The typical smokeless powder improvised explosive device, a pipe bomb, is roughly 10 inches long and 1 inch wide and contains approximately ½ pound of powder. The materials used for these devices are cheap and readily obtainable at commercial establishments. Smokeless powder is attractive for use in improvised explosive devices, because it is readily available and has the potential for a powerful explosion when the powder is placed in a closed container (National Research Council 1998). Larger explosive devices usually use bulk materials such as ammonium nitrate and fuel oil, typically purchased in greater quantity at an even cheaper price.
Many types of containers are used in the construction of smokeless powder bombs (National Research Council 1998). Whereas metal pipes are most common, plastic pipes, cans, CO2 cartridges, and glass or plastic bottles have been used. These containers are often placed within larger packages for ease of transport and concealment.
Another important part of the powder bomb is the initiation system, which provides the impetus to start the powder burning within its container (National Research Council 1998). A few examples include cigarettes, matches, and safety fuses (Scott 1994; Stoffel 1972). Improvised explosive devices utilizing smokeless powders within a robust container often include an initiation system, as shown in Figure 2 (Scott 1994).
Using data from the National Research Council on reported actual and attempted bombings using propellants during the five-year period from 1992-1996, Table 2 illustrates an average of 653 incidents per year involving the use of black and smokeless powders. Bombs containing black or smokeless powders were responsible for an average yearly count of about 10 deaths, 83 injuries, and almost $1 million in property damage for each of the five years. Using the National Research Council's data involving devices filled with black and smokeless powders, Table 3 illustrates the number of actual bombings that caused at least one death, one injury, or a minimum of $1,000 in property damage, as well as attempted bombings aimed at significant targets (National Research Council 1998).
Type of Explosive Used
|Bomb containing smokeless powder/ black powder/black powder substitutes|
Property damage costs
NOTE: Actual and attempted bombings include incidents in which a device either exploded or was delivered to a target but did not explode. It does not include unexploded devices that were recovered by law enforcement personnel but not associated with a target.
Number of Incidents
|Total incidents|| |
Table 3. Significant Actual and Attempted Bombings Involving Devices Using Smokeless Powder, Black Powder, or Black Powder SubstitutesAnalysis
NOTE: Significant bombings represent actual bombings that caused at least one death, one injury, a minimum of $1,000 in property damage, or attempted bombings aimed at specified targets.
Many methods for the analysis of smokeless powders have appeared over the years. These procedures have been extensively reviewed in a number of recent texts (Beveridge 1998; National Research Council 1998; Yinon and Zitrin 1993). The initial characterization of the powders is assessed using powder morphology and spot tests. Various instrumental analytical techniques allow organic additives such as nitroglycerine, diphenylamine, ethyl centralite, dinitrotoluene, and various phthalates to be detected and quantitated. These materials are usually analyzed using gas chromatography-mass spectrometry (Martz and Lasswell 1983) and liquid chromatography (Bender 1983; McCord and Bender 1998). illustrates the analysis of an IMR 700X powder using gradient high performance liquid chromatography (Wissinger and McCord 2002). More recently, methods involving capillary electrophoresis have also been shown to be effective (Northrop et al. 1991; Smith et al. 1999). Fourier transform infrared microscopy can be used for the identification of nitrocellulose (Zitrin 1998).
The process of manufacturing smokeless powders provides sources of inorganic ions that are present in postblast residue. These can be analyzed by ion chromatography. Although not unique to propellants, the presence of these ions can be used in forensic analysis to aid in the identification of the unknown powder. Potassium sulfate, sodium sulfate, potassium nitrate, barium nitrate, and other salts may be added during the processing of the powder. Nitrate, sulfate, hydrogen sulfide, chloride, and nitrite may appear as a result of the reactions for treating the cellulose to obtain nitrocellulose (Radford Army Ammunition Plant 1987). illustrates the analysis of H414 smokeless powder using ion chromatography. Also documented has been the presence of various cations found in the residue of smokeless powders after deflagration (Hall and McCord 1993; Miyauchi et al. 1998).
The wide variety of chemical components and the different morphologies of smokeless powders present a challenge for the forensic investigator. Physical characteristics of partially burned and unburned powder as well as the organic and inorganic materials that remain must be considered in the analysis of postblast residue. Although there are many techniques available for the determination of components in smokeless powder residue, the various formulations of powders make it necessary to continue the advancement of existing analyses and to develop new methods for testing the full range of available smokeless powders.
What causes Diabetes? Why should you get Pre Diabetes?
Will it become Type 2 diabetes in you? Can you prevent it?
The why and how of prediabetes is explained here in the light of scientific facts.
The worry starts, when you become older and pre diabetes transposes into Type 2 Diabetes. Then it becomes a life long struggle for you to control your diabetes and prevent its complications.
ConfirmationPre-Diabetes means predisposed to acquire severe diabetes. When the disease is in its early form, you may not worry much about it. When you are young, you have got a lot of steam left in you.
Supposing your diagnosis confirms your pre diabetes. Your doctor tells you that prediabetes is a warning sign and a precursor for diabetes type 2. He also tells you to better take care to prevent it.
It is then you look for explanations for what causes Pre Diabetes. To understand this, you must know what is digestion and glucose metabolism. And know how glucose becomes energy, and about the role of insulin.
You must also know about the importance of liver and the correct glucose levels. When you understand these, you will know what causes this diabetes, and prevent the risks of your promotion to diabetes type 2.
Energy SecretsYou know that you get energy from food. Food is broken down into carbohydrates, proteins and fat. The carbohydrates are broken down into glucose. It is absorbed in blood. Your cells produce energy from glucose.
Glucose is absorbed in your body cells to produce energy, through ATP. Any disturbance in this process causes your pre diabetes.
Sixty Trillion CellsEach cell in your body works like a factory to produce energy from glucose. Your body has sixty trillions cells. Each cell absorbs glucose from your blood and produces energy. This is the result of glucose metabolism.
The glucose comes from your blood stream. A hormone called insulin, which is secreted from your pancreas, helps this glucose to enter your body cells. These cells accept glucose through their membrane walls.
Glucose & Energy
This happens when these cells respond well to your insulin. This way, glucose enters inside your cellular factories, energy is produced from glucose and the level of glucose in your blood stream comes down.
When this process is impaired, it becomes one of your causes for your pre diabetes. Cells resist absorption of glucose, levels of glucose increases in your blood stream and you develop symptoms of prediabetes.
If due to some reasons, enough glucose does not enter your body cells, a situation arises when very little of glucose gets into the cells and too much of it is left behind in your blood stream. What are those reasons?
Insulin makes your cells absorb glucose. If it is insufficient, necessary glucose does not enter your cells. It leads to high blood glucose levels. This explains high blood glucose, and how you got your pre diabetes.
If your pancreas is damaged by virus, heredity or genetics, it may not produce enough insulin. Or though sufficient, it is altered to be incompatible to your body cells. These cells do not respond to your insulin.
In both cases, glucose entry into your cells is restricted, more glucose stays back in your blood and all these cause your pre diabetes.
High BP & Cholesterol
If you have hyper tension, it can cause your Pre diabetes. If you have high cholesterols of the LDL type, and have low amount of the HDL type, and when you have high triglycerides, you are prone to get prediabetes.
It is further confirmed by clinical examinations, that high blood pressure, unsafe cholesterol levels, high triglycerides and the metabolic syndrome are contributing factors for your prediabetes.
Aging & Obesity
Generally, after forty years of age, people tend to be more inactive, more likely to put on weight and the natural body defenses are blunted by the aging process. This can also lead to your pre diabetes.
Obesity and being over weight can be powerful reasons for what causes prediabetes in you. you have more fat tissue in your body which makes your cells resistant to insulin. That is how you develop prediabetes.
Gestational & PolycysticIf you had gestational diabetes in one pregnancy, your risk for developing diabetes again is more, even after your disease disappears. You may develop diabetes type 2 or pre diabetes.
Women who suffer from polycystic ovary syndrome, tend to be obese and their body cells are more resistant to insulin. Polycystic ovary syndrome can be the powerful reason for what causes diabetes in them.
Idle Life & Heredity
Suppose you lead an idle life with out much activity. As you do not burn much glucose, your body cells need less of it. In the long run they become insensitive to it.This is one of the reasons for what causes diabetes.
If your forefathers had diabetes, you will be prone to get prediabetes. People of certain races get prediabetes than people of other races. Heredity, racial factors and aging can also be the reasons.
Why Others Fail?
Unable to diagnose and being unaware of these root causes, the other systems do not take any steps to correct these defects. That is precisely why these systems fail to cure prediabetes and most of your diseases.
Fluorides are organic and inorganic compounds containing the fluorine element. Only inorganic fluorides are the focus of this study, particularly those which are most present in the environment and may affect living organisms.
Generally colourless, the different fluoride compounds are more or less soluble in water and can take the form of a solid, liquid, or gas. Fluorides are important industrial chemicals with a number of uses but the largest uses are for aluminium production, drinking water fluoridation, and the manufacture of fluoridated dental preparations.
How are fluorides released into the environment?
Fluorides are released into the environment naturally through the weathering and dissolution of minerals, in emissions from volcanoes and in marine aerosols. Fluorides are also released into the environment via coal combustion and process waters and waste from various industrial processes, including steel manufacture, primary aluminium, copper and nickel production, phosphate ore processing, phosphate fertilizer production and use, glass, brick and ceramic manufacturing, and glue and adhesive production. The use of fluoride-containing pesticides as well as the controlled fluoridation of drinking-water supplies also contribute to the release of fluoride from anthropogenic sources. Based on available data, phosphate ore production and use as well as aluminium manufacture are the major industrial sources of fluoride release into the environment.
Where in the environment can fluorides be found?
Fluorides in the atmosphere may be in gaseous or particulate form. Atmospheric fluorides can be transported over large distances as a result of wind or atmospheric turbulence or can be removed from the atmosphere via wet and dry deposition or hydrolysis. Fluoride compounds, with the exception of sulfur hexafluoride, are not expected to remain in the troposphere for long periods or to migrate to the stratosphere. Sulfur hexafluoride has an atmospheric residence time ranging from 500 to several thousand years. The transport and transformation of fluoride in water are influenced by pH, water hardness and the presence of ion-exchange materials such as clays. Fluoride is usually transported through the water cycle complexed with aluminium. The transport and transformation of fluoride in soil are influenced by pH and the formation of predominantly aluminium and calcium complexes. Adsorption to the soil solid phase is stronger at slightly acidic pH values (5.5–6.5). Fluoride is not readily leached from soils. The uptake of fluoride by biota is determined by the route of exposure, the bioavailability of the fluoride and the uptake/excretion kinetics in the organism. Soluble fluorides are bioaccumulated by some aquatic and terrestrial biota. However, no information was identified concerning the biomagnification of fluoride in aquatic or terrestrial food-chains. Terrestrial plants may accumulate fluorides following airborne deposition and uptake from soil.
How much fluoride is there in environment?
Fluoride levels in surface waters vary according to location and proximity to emission sources. Surface water concentrations generally range from 0.01 to 0.3 mg/litre. Seawater contains more fluoride than fresh water, with concentrations ranging from 1.2 to 1.5 mg/litre. Higher levels of fluoride have been measured in areas where the natural rock is rich in fluoride, and elevated inorganic fluoride levels are often seen in regions where there is geothermal or volcanic activity (e.g., 25–50 mg fluoride/litre in hot springs and geysers and as much as 2800 mg/litre in certain East African Rift Valley lakes). Anthropogenic discharges can also lead to increased levels of fluoride in the environment. Airborne fluoride exists in gaseous and particulate forms, which are emitted from both natural and anthropogenic sources. Fluoride released as gaseous and particulate matter is deposited in the general vicinity of an emission source, although some particulates may react with other atmospheric constituents. The distribution and deposition of airborne fluoride are dependent upon emission strength, meteorological conditions, particulate size and chemical reactivity. In areas not in the direct vicinity of emission sources, the mean concentrations of fluoride in ambient air are generally less than 0.1 µg/m3. Levels may be slightly higher in urban than in rural locations; however, even in the vicinity of emission sources, the levels of airborne fluoride usually do not exceed 2–3 µg/m3. In areas of China where fluoride-rich coal is used as a source of fuel, reported concentrations of fluoride in ambient air have reached 6 µg/m3. Fluoride is a component of most types of soil, with total fluoride concentrations ranging from 20 to 1000 µg/g in areas without natural phosphate or fluoride deposits and up to several thousand micrograms per gram in mineral soils with deposits of fluoride. Airborne gaseous and particulate fluorides tend to accumulate within the surface layer of soils but may be displaced throughout the root zone, even in calcareous soils. The clay and organic carbon content as well as the pH of soil are primarily responsible for the retention of fluoride in soils. Fluoride in soil is primarily associated with the soil colloid or clay fraction. For all soils, it is the soluble fluoride content that is biologically important to plants and animals.
How much fluoride can be found in living organisms?
Fluorides can be taken up by aquatic organisms directly from the water or to a lesser extent via food. Fluorides tend to accumulate in the exoskeleton or bone tissue of aquatic animals. Mean fluoride concentrations of >2000 mg/kg have been measured in the exoskeleton of krill; mean bone fluoride concentrations in aquatic mammals, such as seals and whales, ranged from 135 to 18 600 mg/kg dry weight. Fluoride levels in terrestrial biota are higher in areas with high fluoride levels from natural and anthropogenic sources. Lichens have been used extensively as biomonitors for fluorides. Mean fluoride concentrations of 150–250 mg/kg were measured in lichens growing within 2–3 km of fluoride emission sources, compared with a background level of <1 mg fluoride/kg. Most of the fluoride in the soil is insoluble and, therefore, less available to plants. However, high soil fluoride concentrations or low pH, clay and/or organic matter can increase fluoride levels in soil solution, increasing uptake via the plant root. If fluoride is taken up through the root, its concentrations are often higher in the root than in the shoot, due to the low mobility of fluoride in the plant. Most fluorides enter plant tissues as gases through the stomata and accumulate in leaves. Small amounts of airborne particulate fluoride can enter the plant through the epidermis and cuticle. Vegetation has been widely monitored in the vicinity of anthropogenic fluoride emission sources. Correlations between fluoride concentrations in vegetation and annual growth increments, wind pattern, distance from fluoride source and hydrogen fluoride concentrations in aerial emissions have been observed. Fluoride accumulates in the bone tissue of terrestrial vertebrates, depending on factors such as diet and the proximity of fluoride emission sources. For example, mean fluoride concentrations of 7000–8000 mg/kg have been measured in the bones of small mammals in the vicinity of an aluminium smelter.
Can fluorides affect health?
Does fluoride affect bones in test animals?
Effects on the skeleton, such as inhibition of bone mineralization and formation, delayed fracture healing and reductions in bone volume and collagen synthesis, have been observed in a variety of studies in which rats received fluoride orally for periods of 3–5 weeks. In medium-term exposure studies, altered bone remodelling, hepatic megalocytosis, nephrosis, mineralization of the myocardium, necrosis and/or degeneration of the seminiferous tubules in the testis were observed in mice administered fluoride in drinking-water (>4.5 mg/kg body weight per day) over a period of 6 months
Does fluoride cause cancer in test animals?
In a comprehensive carcinogenicity bioassay in which groups of male and female F344/N rats and B6C3F 1 mice were administered drinking-water containing up to 79 mg fluoride/litre as sodium fluoride for a period of 2 years, there was no statistically significant increase in the incidence of any tumour in any single exposed group. There was a statistically significant trend of an increased incidence of osteosarcomas in male rats with increasing exposure to fluoride. However, the incidence was within the range of historical controls. Another 2-year carcinogenicity bioassay involving Sprague-Dawley rats exposed to up to 11.3 mg/kg body weight per day in the diet also found no statistically significant increase in the incidence of osteosarcoma or other tumours. Another study, which reported an increased incidence of osteomas in mice receiving up to 11.3 mg/kg body weight per day, is difficult to interpret, because the animals were infected with Type C retrovirus
Does fluoride cause genetic mutations in cells or test animals?
In general, fluoride is not mutagenic in prokaryotic cells. Although fluoride has been shown to increase the frequency of mutations at specific loci in cultured mouse lymphoma and human lymphoblastoid cells, these mutations are likely due to chromosomal damage rather than point mutations. Fluoride has been shown to be clastogenic in a variety of cell types. The mechanism of clastogenicity has been attributed to the effect of fluoride upon the synthesis of proteins involved in DNA synthesis and/or repair, rather than direct interaction between fluoride and DNA. In most studies in which fluoride was administered orally to rodents, there was no effect upon sperm morphology or the frequency of chromosomal aberrations, micronuclei, sister chromatid exchange or DNA strand breaks. However, cytogenetic damage in bone marrow or alterations in sperm cell morphology were reported when the substance was administered to rodents by intraperitoneal injection.
Does fluoride affect reproduction or development in test animals?
Reproductive or developmental effects were not observed in recent studies in which laboratory animals were administered fluoride in drinking-water. However, histopathological changes in reproductive organs have been reported in male rabbits administered (orally) 4.5 mg fluoride/kg body weight per day for 18–29 months, in male mice administered (orally) >4.5 mg fluoride/kg body weight per day for 30 days and in female rabbits injected subcutaneously with >10 mg fluoride/kg body weight per day for 100 days. Adverse effects on reproductive function have been reported in female mice administered (orally) >5.2 mg fluoride/kg body weight per day on days 6–15 after mating and in male rabbits administered (orally) >9.1 mg fluoride/kg body weight per day for 30 days.'
To what extent can fluoride exposure be harmful to organisms in the environment?
What levels of fluoride exposure are harmful to aquatic organisms?
Fluoride did not affect growth or chemical oxygen demand degrading capacity of activated sludge at concentrations of 100 mg/litre. The EC50 for inhibition of bacterial nitrification was 1218 mg fluoride/litre. Ninety-six-hour EC50s, based on growth, for freshwater and marine algae were 123 and 81 mg fluoride/litre, respectively. Forty-eight-hour LC50s for aquatic invertebrates range from 53 to 304 mg/litre. The most sensitive freshwater invertebrates were the fingernail clam (Musculium transversum), with statistically significant mortality (50%) observed at a concentration of 2.8 mg fluoride/litre in an 8-week flow-through experiment, and several net-spinning caddisfly species (freshwater; family: Hydropsychidae), with "safe concentrations" (8760-h EC0.01s) ranging from 0.2 to 1.2 mg fluoride/litre. The brine shrimp (Artemia salina) was the most sensitive marine species tested. In a 12-day static renewal test, statistically significant growth impairment occurred at 5.0 mg fluoride/litre. Ninety-six-hour LC50s for freshwater fish range from 51 mg/litre (rainbow trout, Oncorhynchus mykiss) to 460 mg/litre (threespine stickleback, Gasterosteus aculeatus). All of the acute toxicity tests (96 h) on marine fish gave results greater than 100 mg/litre. Inorganic fluoride toxicity to freshwater fish appears to be negatively correlated with water hardness (calcium carbonate) and positively correlated with temperature. The symptoms of acute fluoride intoxication include lethargy, violent and erratic movement and death. Twenty-day LC50s for rainbow trout ranged from 2.7 to 4.7 mg fluoride/litre in static renewal tests. "Safe concentrations" (infinite hours LC0.01s) have been estimated for rainbow trout and brown trout (Salmo trutta) at 5.1 and 7.5 mg fluoride/litre, respectively. At concentrations of >3.2 (effluent) or >3.6 (sodium fluoride) mg fluoride/litre, the hatching of catla (Catla catla) fish eggs was delayed by 1–2 h. Behavioural experiments on adult Pacific salmon (Oncorhynchus sp.) in soft-water rivers indicate that changes in water chemistry resulting from an increase in the fluoride concentration to 0.5 mg/litre can adversely affect migration; migrating salmon are extremely sensitive to changes in the water chemistry of their river of origin.
What levels of fluoride exposure are harmful to microbes and plants?
In laboratory studies, fluoride seems to be toxic for microbial processes at concentrations found in moderately fluoride polluted soils; similarly, in the field, accumulation of organic matter in the vicinity of smelters has been attributed to severe inhibition of microbial activity by fluoride. Signs of inorganic fluoride phytotoxicity (fluorosis), such as chlorosis, necrosis and decreased growth rates, are most likely to occur in the young, expanding tissues of broadleaf plants and elongating needles of conifers. The induction of fluorosis has been clearly demonstrated in laboratory, greenhouse and controlled field plot experiments. A large number of the papers published on fluoride toxicity to plants concern glasshouse fumigation with hydrogen fluoride. Foliar necrosis was first observed on grapevines (Vitis vinifera) exposed to 0.17 and 0.27 µg/m3 after 99 and 83 days, respectively. The lowest-observed-effect level for leaf necrosis (65% of leaves) in the snow princess gladiolus (Gladiolus grandiflorus) was 0.35 µg fluoride/m3. Airborne fluoride can also affect plant disease development, although the type and magnitude of the effects are dependent on the specific plant–pathogen combination. Several short-term solution culture studies have identified a toxic threshold for fluoride ion activity ranging from approximately 50 to 2000 µmol fluoride/litre. Toxicity is specific not only to plant species, but also to ionic species of fluoride; some aluminium fluoride complexes present in solution culture may be toxic at activities of 22–357 µmol fluoride/litre, whereas hydrogen fluoride is toxic at activities of 71–137 µmol fluoride/litre. A few studies have been carried out in which the fluoride exposures have been via the soil. The type of soil can greatly affect the uptake and potential toxicity of fluorides. Aluminium smelters, brickworks, phosphorus plants and fertilizer and fibreglass plants have all been shown to be sources of fluoride that are correlated with damage to local plant communities. Vegetation in the vicinity of a phosphorus plant revealed that the degree of damage and fluoride levels in soil humus were inversely related to the distance from the plant. Average levels of fluoride in vegetation ranged from 281 mg/kg in severely damaged areas to 44 mg/kg in lightly damaged areas; at a control site, the fluoride concentration was 7 mg/kg. Plant communities near an aluminium smelter showed differences in community composition and structure due partly to variations in fluoride tolerance. However, it must be noted that, in the field, one of the main problems with the identification of fluoride effects is the presence of confounding variables such as other atmospheric pollutants. Therefore, care must be taken when interpreting the many field studies on fluoride pollution.
What levels of fluoride exposure are harmful to birds and mammals?
In birds, the 24-h LD 50 was 50 mg/kg body weight for 1-day-old European starling (Sturnus vulgaris) chicks and 17 mg/kg body weight for 16-day-old nestlings. Growth rates were significantly reduced at 13 and 17 mg fluoride/kg body weight (the highest doses at which growth was monitored). Most of the early work on mammals was carried out on domesticated ungulates. Fluorosis has been observed in cattle and sheep. The lowest dietary level observed to cause an effect on wild ungulates was in a controlled captive study with white-tailed deer (Odocoileus virginianus) in which a general mottling of the incisors characteristic of dental fluorosis was noted in the animals at the 35 mg/kg diet dose. The original findings of fluoride effects on mammals were from studies in the field on domestic animals such as sheep and cattle. Fluoride can be taken up from vegetation, soil and drinking-water. Tolerance levels have been identified for domesticated animals, with the lowest values for dairy cattle at 30 mg/kg feed or 2.5 mg/litre drinking-water. Incidents involving domesticated animals have originated both from natural fluoride sources, such as volcanic eruptions and the underlying geology, and from anthropogenic sources, such as mineral supplements, fluoride-emitting industries and power stations. Symptoms of fluoride toxicity include emaciation, stiffness of joints and abnormal teeth and bones. Other effects include lowered milk production and detrimental effects on the reproductive capacity of animals. The lowest dietary concentration of fluoride to cause fluorosis in wild deer was 35 mg/kg. Investigations of the effects of fluoride on wildlife have focused on impacts on the structural integrity of teeth and bone. In the vicinity of smelters, fluoride-induced effects, such as lameness, dental disfigurement and tooth damage, have been found.
What effects have actually been seen in humans?
Has fluoride exposure caused cancer?
Epidemiological investigations on the effects of fluoride on human health have examined occupationally exposed workers employed primarily in the aluminium smelting industry and populations consuming fluoridated drinking-water. In a number of analytical epidemiological studies of workers occupationally exposed to fluoride, an increased incidence of lung and bladder cancer and increased mortality due to cancer of these and other sites have been observed. In general, however, there has been no consistent pattern; in some of these epidemiological studies, the increased morbidity or mortality due to cancer can be attributed to the workers’ exposure to substances other than fluoride. The relationship between the consumption of fluoridated drinking-water and morbidity or mortality due to cancer has been examined in a large number of epidemiological studies, performed in many countries. There is no consistent evidence of an association between the consumption of controlled fluoridated drinking-water and increased morbidity or mortality due to cancer.
What are the effects on teeth and bones?
Fluoride has both beneficial and detrimental effects on tooth enamel. The prevalence of dental caries is inversely related to the concentration of fluoride in drinking-water. The prevalence of dental fluorosis is highly associated with the concentration of fluoride, with a positive dose–r esponse relationship. Cases of skeletal fluorosis associated with the consumption of drinking-water containing elevated levels of fluoride continue to be reported. A number of factors, such as nutritional status and diet, climate (related to fluid intake), concomitant exposure to other substances and the intake of fluoride from sources other than drinking-water, are believed to play a significant role in the development of this disease. Skeletal fluorosis may develop in workers occupationally exposed to elevated levels of airborne fluoride; however, only limited new information was identified. Evidence from several ecological studies has suggested that there may be an association between the consumption of fluoridated water and hip fractures. Other studies, however, including analytical epidemiological investigations, have not supported this finding. In some cases, a protective effect of fluoride on fracture has been reported. Two studies permit an evaluation of fracture risk across a range of fluoride intakes. In one study, the relative risks of all fractures and of hip fracture were elevated in groups drinking water with >1.45 mg fluoride/litre (total intake >6.5 mg/day); this difference reached statistical significance for the group drinking water containing >4.32 mg fluoride/litre (total intake 14 mg/day). In the other study, an increased incidence of fractures was observed in one age group of women exposed to fluoride in drinking-water in a non-dose-dependent manner.
Has fluoride caused other health problems?
Epidemiological studies show no evidence of an association between the consumption of fluoridated drinking-water by mothers and increased risk of spontaneous abortion or congenital malformation. Other epidemiological investigations of occupationally exposed workers have provided no reasonable evidence of genotoxic effects or systemic effects upon the respiratory, haematopoietic, hepatic or renal systems that may be directly attributable to fluoride exposure per se.
Monday, November 1, 2010
Definitions:Crime Scene Reconstruction- The use of scientific methods, physical evidence, deductive reasoning and their interrelationships to gain explicit knowledge of the series of events that surround the commission of a crime.
Criminal Profiling- The application of psychological theory to the analysis and reconstruction of the forensic evidence that relates to an offender's crime scenes, victims and behaviors.
While both of these activities may appear to be similar and are in fact related, it is important to note that they are not the same. The difference between the two is most easily understood by looking at which questions about the crime they attempt to answer. Crime Scene Reconstruction looks at the physical evidence and attempts to determine "What happened?" and "How did it happen?". Criminal Profiling looks at the physical evidence and the reconstruction and attempts to determine "Why may this have happened?" and "What does that tell us about Who may have done it?". It is important to keep in mind that only those directly involved in the crime know for sure what happened and why, and they may be unable or unwilling to say.
Why is it important to reconstruct the crime prior to profiling the offender? The answer is simple; until you know what happened, and how it happened (at least as much as possible), you have no basis for attempting to determine why and who.
This paper is intended as an overview of the types of reconstruction which may be possible and is not all inclusive (the number and types of things that may be reconstructed is like types of physical evidence- nearly limitless). For more specific information check the references or contact an expert in the field in question.
Types of Reconstruction
(Lee, pp. 192-3, lists 5 categories of reconstruction; one deals only with the amount of reconstruction done, and another lists several activities including criminal profiling which are not truly reconstruction).
- Specific Incident Reconstruction (Traffic Accident, Homicide, Bombing, etc.).
- Specific Event Reconstruction (Sequence, Direction, Condition, Relation, Identity).
- Specific Physical Evidence Reconstruction (Firearms, Blood, Glass etc.).
In any given scene it may be possible to do a total or only partial reconstruction, and the reconstruction may use more than one technique (i.e. both trajectory and blood stain pattern reconstruction to locate the position of the victim). Some scenes lend themselves to reconstruction better than others. Traffic accidents are common scenes to reconstruct and often can be thoroughly reconstructed. Vehicles are rather massive objects that obey the laws of motion and often leave a wealth of physical evidence behind before, during and after an accident. It may be possible to show the entire sequence of events from the time the vehicles first enter the area of the accident until they come to rest following the accident.
Scenes involving the movement of people are more difficult. While it may be possible to say where a person was in the scene at several points in time, the manner in which they moved in the scene cannot be reconstructed. People may move slowly, quickly, hesitantly, jump up and down, run, skip, fall down, etc. all without leaving any particular trace behind. That said, there are of course the odd cases where the amount and type of physical evidence does allow the paths of the participants to be tracked with some accuracy; however, the vagaries of facial expression, gestures, and body language are simply impossible to reconstruct at all.
Below are some examples of the types of information which reconstruction may provide, again, this is not an all inclusive list. Some items also appear in more than one category, and it may be possible to use information from several areas to complete or validate the final reconstruction.
Examples of Types of Reconstruction:
- Blood and Blood Stain Pattern Analysis
- Identity of victim/offender.
- Position and location of the victim.
- Position and location of the offender.
- Movement by the victim/offender in the scene.
- May identify the location of the scene (if the victim is removed and left elsewhere).
- May indicate a staged or secondary scene.
- Minimum number of blows struck.
- Type of weapon used.
- Reassemble torn/shredded papers.
- Recovery of obliterated writing.
- Shooting distance.
- Position and location of the victim.
- Position and location of the offender.
- Sequence of shots.
- Direction of shots.
- Possibility that the wound(s) could have been self-inflicted.
- Identification of weapon used may link serial cases.
- Functional Evidence
- Does the weapon or vehicle function properly?
- Semi-automatic with slide locked back may indicate last round was fired.
- TV or coffee pot on at scene.
- Do door/window locks properly secure?
- Direction of break (from which side of the glass).
- Sequence of shots (it should be noted that current research indicates that sequencing of shots through laminated automotive glass is not reliable).
- Impression Evidence (Fingerprints, shoe prints, tire tracks).
- Identity of victim/offender.
- Place victim/offender at the scene and at specific sites in the scene.
- Fingerprints may indicate where the offender/victim was in the scene or how an object was held.
- Shoe prints may show location in and movement through the scene.
- Tire tracks may show vehicle position and direction of travel and may indicate the type of vehicle driven.
- Type of ligature used (if missing).
- Use of same/similar ligature can be used to link serial cases.
- Type of ligature used may indicate offender's occupation or interests. (i.e. rope tied with knots commonly used by dock workers or climbers).
- Manner of death (Homicide, Suicide, Natural, Accidental).
- Time of death (approximate).
- Cause of death/weapon used.
- Time before incapacitation from wounds (approximate).
- Whether injuries were sustained pre- or post-mortem.
- Identity and/or age of victim.
- Was victim sexually assaulted, and in what manner.
- Possibility that the wound(s) could have been self-inflicted.
- Physical Match (Reassembly of broken objects).
- Vehicle lamps, mirrors and windows.
- Aircraft which have crashed and/or exploded.
- Relational/Positional Evidence
- Blood drops on the threshold of a door indicates that the door was open when the blood was shed.
- Location of other objects and their condition may also indicate a variety of things depending on the specifics of the crime.
- Trace Evidence
- Trajectory of projectiles based on retention of material through which they have passed.
- Place offender/victim at the scene, and at specific sites in the scene.
- Describe the environment of an unknown crime scene.
- May indicate offender occupation.
- Vehicle positions, speeds, sequence of accident events.
Information Needed for Reconstruction
Generally speaking it is best to go to the scene, preferably at the time of the incident. Information may come from physical evidence, witness statements, and the reports of other experts. The reconstructionist should examine all scene photographs, autopsy protocol and photographs, measurements, drawings, notes, reports and items of evidence. Complete and accurate documentation of the scene is essential. Depending on the type of reconstruction being done this may include some different things such as the height and vertical/horizontal angles of shots into a wall, or the length and width of a bloodstain.
Steps in Reconstruction
- Recognition of evidence.
- Documentation of evidence.
- Collection of evidence.
- Evaluation of evidence.
Step 1, recognition of evidence, is arguably the most important, as Lee points out "Unless the potential evidence can be recognized, no further reconstruction can be carried out."
Steps 1-3, recognition, documentation and collection of evidence, are the heart of any successful scene investigation, and form the basis for the reconstruction.
Step 4, evaluation of evidence, examines the evidence (possibly following laboratory analysis) and looks at what information the evidence provides, and how reliable it is. At this time any witness statements should be compared to the evidence to see which parts of the statements can be supported or refuted by the evidence.
Step 5, hypothesis, is the formulation of an idea of how the event(or portions of it) occurred. This is not merely conjecture and should be firmly supported by the evidence.
Step 6, testing, looks to see how the hypothesis developed in 5 can be validated. This is accomplished by checking the evidence against known physical laws or devising a test to attempt to replicate the event(or the relevant segment).
Step 7, reconstruction, is the reporting of the results of the analysis. The results are reported as a range, where the event(or portions of it):
- Can be shown to have occurred in a given manner.
- Can be shown to be likely to have occurred in a given manner.
- Can be shown to be unlikely to have occurred in a given manner.
- Can be shown not to have occurred in a given manner.
Application to Profiling
The reconstruction forms the foundation from which the profiler can begin. The reconstruction provides answers about what happened and how it happened. From there the profiler can begin asking "Why?" questions. Questions of "Why?" are not answered by the reconstruction. Neither are questions of Intent and Motive. Attempts to answer these questions may be investigatively useful, but lack the firm support of evidence required of reconstruction. Authors on both reconstruction and profiling speak of mentally re-enacting the events of the crime; again, this can be investigatively useful, but is not reconstruction.
As profiling is intended as an investigative tool, it attempts to go beyond the reconstruction, and answer questions of intent and motivation. From these admittedly subjective answers it can provide a clearer picture of the offender.
As an example, take a scene where the reconstruction shows as Event 1- "Subject breaks into residence through rear window. Window lock was previously secured and was jimmied with a thin, wide, black metal pry bar." Based on this information the profiler can begin to look at "Why?". Why did the offender choose this window? Why did he use this method of entry? Has it worked for him in the past? Where did he get the pry bar? Did he bring it with him or acquire it at the scene? The profiler can continue in this fashion through the scene, looking at the known facts, and then attempting to address the motivations behind the known actions. Working through the scene in this manner will also serve to highlight both the Modus Operandi and Signature aspects of the crime.
- Modus Operandi is the "method of operation", those things that the offender does which are necessary for the completion of the crime (method of entry, use of a weapon to control the victim, etc.).
- Signature is defined as those things done by the offender which are not necessary for the completion of the crime, but which the offender must do to satisfy himself (use of complex ligature, sadism, etc.).40
The reconstruction may show a sequence of events or actions that are unnecessary in the commission of the crime. In serial cases the recurrence of the same sequence at multiple scenes, or the modification of parts of it, may also assist in this determination.
A Case Study: The Murder of Donna Lynn Vetter
Donna Lynn Vetter was a 22-year old, white female. She worked as a stenographer for the FBI field office in San Antonio, Texas. On September 4, 1986, she was raped and murdered in her apartment. Ms. Vetter was last seen alive at 9:10PM, by a neighbor. She was found dead at 10:35PM; this places the occurrence of the offense to within a period of just over one hour. During this time the following events took place:
- Offender enters the apartment by pulling out the screen on the otherwise unsecured front window, knocking over a plant on his way in.
- Offender unplugs the telephone.
- Initial contact between the offender and the victim occurs near the bathroom. Victim is struck in the face.
- Assault continues in the kitchen area where the offender obtains a knife. The victim is stabbed repeatedly and her clothing cut and/or torn off.
- Offender drags the victim from the kitchen, through the dining room into the living room, leaving a blood trail along the way.
- Offender sexually assaults the victim in the living room.
- Offender hides the knife under a seat cushion in the living room.
- Offender leaves the scene.
- Unplugging the telephone (which is unnecessary if he intends to kill the victim).
- Blitz type assault intended to render the victim compliant.
- Use of a weapon of opportunity (i.e. the kitchen knife), rather than one brought to the scene by the offender.
- The fact that nothing was stolen from the apartment.
In this case the victim's continuing resistance led to an escalation of violence and ultimately to her death. When combined with the victimology and geoforensic information, the reconstruction allowed a thorough profile of the offender to be completed. 41,42
Conclusion: The Importance of Competent Crime Scene Work in Reconstruction and Profiling
Unless the analyst (reconstructionist or profiler) is one of the scene investigators, the basic scene work will likely already be completed, and any deficiencies will probably be impossible to correct. This may limit the information which the analyst can provide. To this end the need for continuing/advanced training for scene investigators cannot be overstated. While much of the evidence used for reconstruction speaks for itself and can be documented and collected using standard crime scene procedures, some types of reconstruction require specialized information.
The main three types would be Blood Stain Pattern, Traffic Accident, and Trajectory Reconstruction. All three types require specialized knowledge of what evidence to look for at the scene, and what documentation (photographs, measurements, etc.) are required to utilize the evidence in reconstruction.
An investigator at a traffic accident must know the difference between skid and yaw marks, for example. He must be able to document that the mark is a yaw rather than a skid, and know that each mark must be measured differently. Measurement of the length of a yaw mark is not much use in reconstruction.
Similarly a photograph of a bullet hole does not allow for trajectory reconstruction. We must know the position, height and angle at least, and knowledge of the direction is helpful.
A great deal of specialized knowledge is required for the proper interpretation of blood stain patterns. Without this knowledge the investigator may not even know what he needs to document, let alone how to do it.
Without competent, thorough scene work, the subsequent analysis may be incomplete or impossible.