Forensic Chemistry Part 3
FINAL CHAPTER OF THE MODULE
Covering the following topic:
[1] Glass Fragments and Glass Fractures
[2] Tool marks and other Impressions: Casting and Molding, and Soil Analysis
[3] Restoration of Tampered Serial Number
[4] Arson
[5] Dangerous Drugs
THE GLASS FRAGMENTS AND GLASS FRACTURES
How do we consider glass and glass fragments as trace evidence when discovered at the crime scene?
The video presentation below will tell us how, so “watch” it and learn!
TOOL MARKS AND OTHER IMPRESSIONS: CASTING AND MOLDING
A TOOL MARK is any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object. Most often, tool marks are encountered at theft and robbery scenes that involve forcible entry into a building or safe. Generally, these marks occur as indented impressions into a softer surface or as abrasion marks caused by the tool cutting or sliding against another object. (Ang tool marks in other words ay gawa ng mga bagay na maaring mag-iwan ng bakas o marka sa pinangyarihan ng krimen; tulad ng hammer, knife, screwdriver, etc.)
This category includes any object suspected of containing the impression of another object that served as a tool in a crime. For example, a screwdriver or crowbar could produce tool marks by being impressed into or scraped along a surface of a wall. There are three major categories of tool marks, they are:
[1] Indentations Marks
Indentations marks are made by a tool when it is pressed against a softer surface, often forming a negative impression on the object receiving the force. Such as the result of the prying action of a screwdriver or crowbar on a door or window. Another example of this is the marks created by the firing pin on the primer because of the blow or action of the hammer on it. Other books named it COMPRESSION MARKS.
[2] Abrasion Marks
Abrasion marks are made when surfaces slide across one another. Other books refer to it as friction, drag or slip, or slide impression. Such marks usually consist of a pattern of parallel striations; class characteristics are more difficult to determine from sliding tool marks unless the tools causing marks had been recovered or discovered.
[3] Cutting Marks
Cutting marks are produced along the edge as a surface is cut. It is a combination of compression and sliding tool marks. The cutting tool indents the material being cut and it does the working surfaces of the tool slide over the cut surfaces.
NOTE: Strictly speaking, FIREARMS IDENTIFICATION is a kind of TOOL MARKS IDENTIFICATION because of the different characters of marks found on both slugs and shells fired in firearms. NOTE FURTHER: More than one type of mark can be made at the same time on a surface.
COMPARING TOOL MARKS
Typically, an indented impression is left on the frame of a door or window or on any surface as a result of the prying action (pagsungkit o pagpwersa) of a screwdriver, crowbar, or pliers. A careful examination of these impressions can reveal important class characteristics—that is, the size and shape of the tool. However, they rarely reveal any significant individual characteristics that could permit the examiner to individualize the mark to a single tool. Such characteristics, when they do exist, usually take the form of discernible random nicks and breaks that the tool has acquired through wear and use (ito at maaring gasgas o pagkapudpod ng tools, tipak o bungi na nagbibigay ng bagong anyo o hitsura sa dulo o blade ng tools na kapag magmarka sa isang bagay makikilala mo na itong tools na ito ang ginamit). TOOL MARKS are produced by instruments like ax, hammer which touch the area only once in producing the impressions. COMPRESSION MARKS are produced by a single application of tools on one area of contact, like a single blow of the hammer on a surface, while FRICTION MARKS are a series of scratches or striations produced by pushing a tool across the surface, such as impression made by an ax.
Just as the machined surfaces of a firearm are impressed with random striations during its manufacture, the edges of a pry bar, chisel, screwdriver, knife, or cutting tool likewise display a series of microscopic irregularities that look like ridges and valleys (kung susuriin daw ang marka gawa ng mga tools nag-iiwan ito ng maliliit (microscopic) na marka tulad ng land and grooves ng barrel ng isang baril). See our example below.
Such markings are left as a result of the machining processes used to cut and finish tools. The shape and pattern of such minute imperfections are further modified by damage and wear during the life of the tool (ang pagkakaroon ng iba’t-ibang anyo ng mukha sa talim o dulo ng isang bagay ay dahil sa mga hindi sinasadyang pagkasira ng tunay na mukha ng tools, gaya ng pagpwersa, pagpalo o paghasa nito habang sya ay ginagamit).
Considering the unending variety of patterns that the hills and valleys can assume, it is highly unlikely that any two tools will be identical. Hence, these minute imperfections impart individuality to each tool (dahil sa mga maliliit na imperfections na yan habang ginagamit ang isang bagay, masisiguro natin na ang bawat tools ay may kanya-kanyang pagkakaiba-iba)
If the edge of a tool is scraped against a softer surface, it may cut a series of striated lines that reflect that pattern of the tool’s edge (see the picture above). Markings left in this manner are compared in the laboratory through a comparison microscope with test tool marks made from the suspect tool. The result can be a positive comparison, and hence a definitive association of the tool with the evidence mark, when a sufficient quantity of striations match between the evidence and test markings.
Watch the short video below and try to analyze the situation; create a mental picture of the crime committed and be able to determine the nature of evidence needed to (possibly) recover by an investigator.
So how do you collect then evidence that may help you solve the crime?
HOW TO COLLECT AND PRESERVE TOOL MARKS AS EVIDENCE
Whenever practical, the entire object or the part of the object bearing a tool mark should be submitted to the crime laboratory for examination. When removal of the tool mark is impractical, the only recourse is to photograph the marked area to scale and make a cast of the mark. Under these circumstances, liquid silicone casting material has been found to be the most satisfactory for reproducing most of the fine details of the mark (tignan ang larawan sa ibaba). However, even under the most optimum conditions, the clarity of many of the tool mark’s minute details will be lost or obscured in a photograph or cast. Of course, this will reduce the chance of individualizing the mark to a
single tool.
The crime-scene investigator must never attempt to fit the suspect tool into the tool mark. Any contact between the tool and the marked surface may alter the mark and will, at the least, raise serious questions about the integrity of the evidence (wag na wag daw susubukan na isukat ang gamit o tools doon sa marka na iniwan dahil baka magdulot ito ng pagbabago sa hitsura o pagkasira nito). The suspect tool and mark must be packaged in separate containers, with every precaution taken to avoid contact between the tool or mark and another hard surface. Failure to properly protect the tool or mark from damage could result in the destruction of its individual characteristics.
There were materials and substances that can be used to develop a PLASTIC COPY OF THE IMPRESSION (just like what is shown below), and this author (Wilber) is a trained Crime Scene Technologist of SIRCHIE International, a leading supplier of criminalistics equipment.
Furthermore, the tool or its impression may contain valuable trace evidence. Chips of paint adhering to the mark or tool provide perhaps the best example of how the transfer of trace physical evidence can occur as a result of using a tool to gain forcible entry into a building. Obviously, the presence of trace evidence greatly enhances the evidential value of the tool or its mark and requires special care in handling and packaging the evidence to avoid losing or destroying these items.
As a continuation of this topic, because we are discussing here IMPRESSION, we will discuss how to treat this kind of evidence that falls in the same class, they are all referring to IMPRESSION. Making a three-dimensional representation of the impression is called casting and molding.
CASTING AND MOLDING
Another method of recording the appearance of evidence in the crime scene is to reproduce its external form in the three dimensions by making casts and if necessary a mold. Thus IMPRESSIONS such as those produce by feet, tires, teeth, and tools can be reproduced by casting and the shape of objects such as weapons, seals or the features of a dead person can be duplicated by casting and subsequently making a mold (dito naidagdag natin na hindi lang tools ang maaring magproduce ng marka o impression, kung hindi pati na ang ngipin sa marka ng kagat [Ted Bundy, the known psychotic criminal in US was convicted because of the dental marks found in the body of one victim] ang paa o sapatos na nag-iwan ng marka sa lupa, ang gulong ng bike, motorsiklo o sasakyan). HOW DO WE DEAL WITH THEM? The basic is the same with tool marks.
Ordinarily, the purpose of making a cast is to enable a scientific comparison to be made with the object suspected of having made the impressions and thus to establish that the object and inferentially its owner was at the scene of the crime (ang dahilan para ito ay gawan ng moulage or cast ay para patunayan ang pagkakaparehas ng marka sa lupa at ng bagay na may gawa nito dahil ito lang ang makapagpapatunay na ang may ari ng marka ay nasa pinangyarihan ng insidente dahil sa doon ito nakita o natagpuan).
MARKS OR IMPRESSIONS AT THE CRIME SCENE
An impression print is made when a print (shoeprint, footprint, tire impression) is left in the mud, sand, or any other soft surface. Generally, a plaster cast is made of the footprint and is then photographed. The photograph of the cast is compared to the shoe in question.
When an impression is found on the crime scene the following order should be followed:
[1] a photograph should be made of the impression;
[2] a plaster cast should be made;
[3] a photograph should be made of the plaster cast;
[4] after a suspect shoe has been recovered the suspect shoe should be photographed;
[5] a comparison should be made between the photographs of the plaster cast and the photograph of the suspect shoe;
NOTE:
What is given here as an example is a shoe impression; As mentioned earlier, that all marks and impressions (tool marks and impression) must be processed in the same manner from the time of their discovery which starts on photographing and sketching, measuring, casting, then collecting by placing it in a proper container. At the laboratory, COMPARISON must be made to establish the IDENTITY or NON-IDENTITY of the marks or impressions.
In doing so, it is the goal of the crime scene investigator to find individual characteristics such as nicks, scars, worn places, and so forth… (makikilala daw ang bagay o instrumento na may gawa ng marka or bakat [impression] sa pamamagitan ng {nicks or scars} pingas, bungi o sugat, {worn places or wears and tears} gasgas o pagkapudpod). Unfortunately, footwear scars may be erased in a short time and thus leave individual characteristics in footprints very soon that might show differences in appearance. An example is a possibility that by accidents new distinctive appearance may appear on the face of the shoe and therefore create a different appearance, or the owner happens to use it on rough surfaces that degrade the appearance of the shoe spikes, or by intent, the owner destroys or removes its surface to avoid detection. Same with the vehicles suspected of creating an impression, that it can be changed deliberately and throw the spare tire elsewhere.
It is through this that additional efforts must be made by the investigator to RECOVER THE TOOLS OR THE MATERIALS THAT CAUSE THE IMPRESSION AS SOON AS POSSIBLE!
HOW TO MAKE MOULAGE?
Although a number of materials can be used to make a cast experience has shown that plaster of paris is the most widely applicable particularly in outdoor scenes (dental plaster can be used also especially if the ground is wet). It is simple to prepare provides a durable cast and is capable of reproducing fine detail.
Preparation
Before the evidentiary indentation or impression is cast, the five noted orders should be followed:
1. Spraying
If the receiving surface consists of a soft substance such as dust, sand, or flour a quick-drying fixative such as plastic spray or shellac should be applied prior to casting. The spray should be directed against a piece of cardboard and permitted to settle over the impression in a form of moisture. Of course, if the surface and the impression are hard, fixative can be directed to the surface. When the fixative is quite dry, a fine layer of machine oil should be sprayed over the surface to facilitate the separation of the cast from the fixative easier.
2. Mixing the plaster
An estimated amount of material required for an inch thick cast should be made and a corresponding quantity of water placed in a glass, porcelain, or rubber container. The plaster is then sprinkled evenly over the surface of the water. The plaster is now stirred thoroughly until the mixture has the consistency of cream. Plaster or water is added to achieve the proper consistency.
3. Pouring
The mixture is poured over the impression at a low level. The fall of the liquid should be broken by means of a flat piece of wood. When a depth of ½ inch is reached the pouring should be interrupted and the cast reinforced by lying on pieces of fine mesh wire or light pieces of wood. The remainder of the plaster is then poured on the first layer.
4. Setting
The cast should be permitted to set for approximately 30 minutes. In hardening, the plaster becomes warm and subsequently colds on the setting. NOTE: Never add sugar because it will slow or retard the setting of the cast; instead a table salt can be added to hasten or to make the setting of the cast quick.
5. Identification
Before the plaster has completely set it should be marked by the investigator for identification. The date, case number, and initials of the investigator can be scratched on the upper surface.
6. Cleaning
After hardening the cast should be removed and permitted to further dry for several hours. It can be washed and lightly brushed to remove the adhering debris.
OTHER DEVELOPING TECHNIQUE
Electrostatic lifting, but this method is not much used or applied in our country due to limited resources (both human and materials and methods). below is an example of electrostatic lifting on the floor (smooth surfaces) and by means of dusting using fluorescent powder.
The electrostatic lifting technique is particularly helpful in recovering barely visible dust prints on colored surfaces. Dust impressions can also be enhanced through chemical development. (This only means na kahit mga alikabok ay pwedeng kunan ng positive copy na kasinghugis [o kamukha] at kaparehas na sukat ng impressing materials)
For TIRE AND SHOE IMPRESSION, Class I dental stone, a form of gypsum (in the absence of plaster of Paris), is widely recommended for making casts of shoe and tire impressions. The cast should be allowed to air-dry for 24 to 48 hours before it is shipped to the forensic science laboratory for examination.
An aerosol product known as Snow Impression Wax is available for casting snow impressions. The recommended procedure is to spray three light coats of the wax at an interval of one to two minutes between layers, and then let it dry for ten minutes. A viscous mixture of Class I dental stone is then poured into the wax-coated impression. After the casting material has hardened, the cast can be removed. (Sa Pilipinas dahil wala tayong snow, di rin ito applicable.
Several chemicals can be used to develop and enhance footwear impressions made with blood. In areas where a bloody footwear impression is very faint or where a subject has tracked through blood, leaving a trail of bloody impressions, chemical enhancement can visualize latent or nearly invisible footwear impressions.
MOULAGE
In reproduction of the shape of an object such as the face of a deceased person, it is necessary to make a mold. Subsequently, a cast is made of the mold. Ordinarily, a colloidal substance is employed to make the mold and a wax composition, which is then used for casting. The occasion on which the investigator will require to employ a moulage method is quite rare; hence the practice of this reproduction technique is usually restricted to the law enforcement laboratory.
MODELING CLAY
For small impressions, such as tool marks, modeling clay will be found to be a satisfactory reproduction medium. Simply pressing the clay into the indentation and removing it makes a cast of impressions. The form of the clay is now that of the object which made the impression. A positive impression can be made from the clay by immersing it in a plaster of Paris. Silicon glue or sealant can also be used in casting impressions on woods and metallic objects for purpose of making a mold.
End of Casting and Molding
SOIL ANALYSIS AND FORENSICS
Forensic Soil Analysis is the use of soil sciences and other disciplines to aid in a criminal investigation. Soils are like fingerprints because every type of soil that exists has unique properties that act as identification markers. This means that the origin of the soil sample can be identified. For example, clay embedded in the sneaker of a criminal can be traced back to a specific clay type found along a lake where a murder victim was discovered. The majority of soil cases involve footprints or tire marks that have been left in the soil. You can now relate our previous topic (CASTING AND MOLDING and Moulage) to this application by simply examining the object that causes the impression of any soils or muds adhering to it.
The unique properties of soil are as follows:
Sediment
The original solid particles that were weathered and transported. This could be in the form of a grain of rock that breaks off of the larger parent material (larger version of rock). Soils can develop on these sediments due to physical and chemical alteration.
Color
Indicates its history as well as the compounds present in the soil. For example, white or gray soil could mean that the soil contains lime or has been leeched((a chemical, a metal, etc.) from a substance by the action of a liquid passing through the substance. Gray soil can also mean that the organic material or moisture is present, black soil suggests the same. Soil that is red, brown, or yellow generally suggests that there is iron present.
Structure
Indicates whether the soil is composed of a single grain particle or not. This is determined by the presence of peds (clumps). These peds are formed due to cementing agents such as calcium carbonate attracting the soil particles so that they adhere to each other to form either bulky peds which are small conglomerates (masses) or platy peds which are flat and sheet-like.
PETROGRAPHY: The systematic description of geological materials, their composition, and organization, in hand specimens and thin sections.
GEOLOGY: Also known as ‘geoscience’ or ‘Earth science’, geology is the study of the structure, evolution, and dynamics of the Earth and its natural mineral and energy resources
In this module, we will be presenting video presentation slides to understand and emphasize the usefulness of soil in forensic investigation.
WATCH THIS!
RESTORATION OF TAMPERED SERIAL NUMBERS
Serial numbers are placed on firearms, machines, jewelry, and any other metallic object during the manufacturing process and generally consist of a combination of letters and numbers or numbers alone. They are unique to an individual object, although there are instances where objects from different manufacturers can have the same serial number, but different styles (like font and sizes).
They provide a means by which law enforcement agencies can trace the origin and registered owner (if applicable). For this reason, they are often obliterated by criminals using methods such as filing, grinding, center-punching, over-stamping, drilling, or welding.
There are a number of techniques that forensic firearms examiners use to restore obliterated markings and they fall into two broad categories, namely, non-destructive and destructive. The choice of restoration technique is determined by the type of metal involved, the process by which the serial number was marked whether by etching, casting, engraving, or stamping, and the method used to obliterate the serial number.
Nondestructive restoration techniques include a visual examination, often with the aid of a low-powered microscope, to establish whether sufficient detail exists to identify individual digits from the remaining portion of the serial number.
Destructive restoration techniques include the use of magnetic particle and acid etching techniques. Chemical acid etching is the most common and successful technique currently in widespread use and can be used with or without heat. The techniques presented here can also be applied to the restoration of serial numbers in other situations such as on car chassis or engine blocks.
In this study, the examiner must have a background in metallography (Metallography is the study of the physical structure and components of metals, by using microscopy) and metallurgy (metallurgy, art, and science of extracting metals from their ores and modifying the metals for use. … It also concerns the chemical, physical, and atomic properties and structures of metals and the principles whereby metals are combined to form alloys) for them to decide what approach will be needed in a PROBLEM INVOLVING METALS.
In this module, we will be presenting a video to expound on the importance of the restoration of embedded numbers (or letters) on metal. WATCH THE VIDEO BELOW!
CHEMISTRY APPLIED IN ARSON
CHEMISTRY APPLIED IN ARSON is simply analyzing fire debris samples with comprehensive two-dimensional gas chromatography. Determining the presence and absence of ignitable liquid residues (ILRs) with confidence. Creating a chemical fingerprint to identify ILR sources and to match across the evidence.
In this module, we will be presenting two videos for you to understand how is FORENSIC CHEMISTRY used in arson investigation. WATCH THE VIDEO BELOW and learn!
Propagation of Fires:
Video Presentation about heat sources, conduction, convection, and radiation: Watch!
DANGEROUS DRUGS
INTRODUCTION
Drugs as a problem is a recognized problem confronting the world. In the Philippines, Republic Act 6425 or the Dangerous Drug Act of 1972 was enacted specifically against this problem. The Dangerous Drug Board (DDB) was created to coordinate the effort of the various government and civic agencies. Anti-Narcotic units were organized to enforce the provisions of this Act.
Because of the emerging trends in drug problems, on the Twelfth Congress during its First Regular Session, the Congress of the Philippines passed a law repealing Republic Act 6425. On June 07, 2002, the President of the Philippines approved Republic Act 9165 (AN ACT INSTITUTING THE COMPREHENSIVE DANGEROUS DRUGS ACT OF 2002 REPEALING REPUBLIC ACT 6425 OTHERWISE KNOWN AS THE DANGEROUS DRUG ACT OF 1972, AS AMENDED, PROVIDING FUNDS THEREFOR, AND FOR OTHER PURPOSES. This law is more known today as the COMPREHENSIVE DANGEROUS DRUG ACT OF 2002 that provides a separate body to enforce and act drug-related problems and violations.
Under the Comprehensive Dangerous Drug Act of 2002, the Dangerous Drug Board shall be the policy-making and strategy-formulating body in the planning and formulation of policies and programs on drug prevention and control. It shall develop and adopt a comprehensive, integrated, unified, balanced national drug abuse prevention and control strategy. It shall be under the office of the President (Art. IX, Sec. 77).
On the other hand, the Philippine Drug Enforcement Agency (PDEA) will carry out the provisions of R.A. 9165, and shall serve as the implementing arm of the Board, and shall be responsible for the efficient and effective law enforcement of all provisions on the dangerous drug and/or controlled precursor and essential chemical provided in this act (Art. IX, Sec. 82).
Though the enforcement arm pertaining to the drugs problem was transferred from the Philippine National Police and National Bureau of Investigation, still their crime laboratory (Crime Lab of both PNP and NBI) conducts an analysis of drugs seized, confiscated, or surrendered.
WHAT ARE EVIDENCE RELATED TO DRUG VIOLATION?
The drugs are received in various forms such as tablets, capsules, powder, bricks or morphine, crushed dried leaves, cigarettes, and plants uprooted or in pots and improvised seedbeds.
Paraphernalia’s like smoking pipes, hypodermic syringes, and needles, and ashtrays are submitted for examination. These may have been confiscated in the person of suspects or discovered accidentally in the false bottom of the luggage. The manner of packaging varies from hastily made paper wrappings to heat-sealed water plastic bags. Blood and urine of suspected drug users are also examined to determine the presence of drug(s) abuse.
NOTE: Other areas of studies about drugs is a separate subject in criminology curriculum, “Drug Education and Vice Control”. You will discuss other important subject matter in such subject separately.
Method of Examination
PRELIMINARY TEST
The suspected drugs submitted are first physically examined to include weighing and counting as appropriate. After which, preliminary tests are conducted to screen the materials. These tests are based on the reaction of the drugs with specific substances or reagents, exhibiting color changes.
They are quite simple to perform even by investigators in the field. In fact, field tests using these techniques are being taught in the Narcotic Investigation Courses. Test kits are commercially available. Some of these tests and reactions noted for the common drugs are summarized below:
CONFIRMATORY TEST
There are several methods available to the chemist to confirm the results of the preliminary tests. A technique much more specific than the color test is microcrystalline examination. A small amount of the drug is dissolved in a few drops of solvent on a slide. Then a reagent is added, forming crystals characteristic of the drug. This is then observed under the microscope.
Microcrystalline tests:
[a] Chemical reagent is added to drug sample on a microscope slide;
[b] A chemical reaction happens, forming a crystalline precipitate on the slide
[c] The sizes and shapes of the crystals are specific to a particular type of drug.
The ultraviolet (UV), infrared (IR) spectrophotometer and the gas chromatograph can also be used for positive identification of drugs. Another method employed is Thin Layer Chromatography (TLC) which is rapid, sensitive and easy to use, and inexpensive (This test is based on color reaction. Below is an example of infrared spectral analysis (methamphetamine) and the picture after it is an example of thin-layer chromatography.
THE MARIJUANA AND ITS CHEMICAL TEST
The Marijuana. The most commonly abused drug is marijuana. The plant is scientifically known as Cannabis Sativa Linn, grows almost anywhere, even in flowerpots. There are three known varieties for this plant, its color is light green in grown plants. Its most identifying features are its leaf, which is formed by an odd number of leaflets. The leaf is shaped like a hand with leaflets representing the fingers. Such leaflet is long, tapering, and pointed, it has a saw-toothed edge. The first leaflet on each side is much smaller than the others like a thumb.
The most common method of use is smoking (see its picture below). The greenish-gray to the brown mixture made from dried tops, leaves, and (occasionally) stalks, is rolled into cigarettes, or used in pipes. It burns with an acrid odor similar to that of burning rope or alfalfa.
Preliminary Test for Marijuana
Observe the fine hairs that appear like bear claws and the spheroidal crystolith (see colored and black & white photo) on its base. This is what marijuana appears on a high-powered microscope.
For dried marijuana ready for use, microscopically, the seeds look like a hulled coconut. Many of the crystolith hairs (b) appear in the shape of bear claws (a) which is not present in any other plant whether resembling or not on the leaves of marijuana. the characteristic bear claws presented by marijuana. The confirmatory test must show the presence of tetrahydrocannabinol (THC), a prominent component of marijuana. To confirm, a drop of diluted hydrochloric acid (20%) is added on the slide with the marijuana specimen and an effervescence appears.
The gas chromatograph and thin-layer chromatography for tetrahydrocannabinol is shown below. While to this date, there are already field tests that can be used for marijuana (see field preliminary test table).
END OF THE MODULE:
END OF FORENSIC CHEMISTRY COURSE
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