Forensic 3 Midterm Notes PDF

**FORENSIC 3: FORENSIC CHEMISTRY AND TOXICOLOGY** ### Textile Fibers In general and broad sense the word "textile" is derived from the Latin word "textillis" and the French "textere", to weave, hence fiber means that can be converted into yarn. A yarn consists of fibers or filaments that have been...

**FORENSIC 3: FORENSIC CHEMISTRY AND TOXICOLOGY** ### Textile Fibers In general and broad sense the word "textile" is derived from the Latin word "textillis" and the French "textere", to weave, hence fiber means that can be converted into yarn. A yarn consists of fibers or filaments that have been twisted together. **Test for textile fibers:** 1. **Burning or Ignition Test** -- It is a preliminary macroscopic examination. A test that determines whether fiber is mineral, animal or vegatble fiber. ### Procedure: a. Manner of burning b. Odor of fumes c. Appearance of burnt end d. Color of ash e. Action of fumes on moisten red and blue litmus paper f. Effect of litmus on a piece of filter paper moistened with lead acetate For **animals fibers** -- fibers smolders or burn slowly and give odor like that of burning feather. When removed from the flame they do not continue to burn readily and a charred bead remains at the end of the fiber. Fumes turn red litmus blue. [Wool] -- odor strong, disagreeable; fumes turn lead acetate paper black or brown. [Silk] -- odor not so pungent, fumes have no effect on lead acetate paper. For **vegetable fibers** -- fibers burn rapidly with a flame and give off but little smoke or fumes. Charred bead not present when fiber is removed from the flame. Fumes turn blue litmus red. 2. **Fluorescent Test** -- Frequently used to determine the general group to which a fiber belongs. It is not reliable for positive identification of fibers. In general, the vegetables fibers exhibit a yellow fluorescence in ultra -- violet light, whereas the animal fibers show bluish fluorescence. ----------------------- -- ------------------- 1\. Unbleached Wool Light yellow 2\. Bleached Wool White 3\. Bleached Cotton White 4\. Mercerized Cotton White 5\. Bleached Linen White 6\. Cuprate Silk Brownish -- white 7\. Viscose Silk Brownish -- white 8\. Nitro Silk Yellowish 9\. Acetate Silk White 10\. Natural Silk White ----------------------- -- ------------------- 3. **Microscopic Examination** -- In general, it is the most reliable and best means identifying fiber. The fiber is placed on a glass slide, teased and covered. g. **Cotton** -- Unicellular filament, flat, ribbon -- like, twisted spirally to right or left on its axis, central canal or lumen broad uniform in diameter; cell wall thick, covered by a thin, structureless, waxy cuticle. Fiber tapers gradually to a blunt or rounded point at one end. h. **Mercerized Cotton** -- Straight, cylindrical, with occasional twists; evenly lustrous, smooth except for occasional transverse folds or wrinkles. Cuticle mostly lacking, lumen irregular in width. i. **Linen** -- Multicellular filament, straight and cylindrical, not twisted and flattened, tapering to a sharp point. Cell wall thick, the lumen appearing as a narrow dark line in the center of the fiber. Filament marked by transverse lines at intervals causing fiber to appear jointed, resembling bamboo. Cross lines frequently interest appearing like the letter x. j. **Cultivated Silk** -- Smooth, cylindrical, lustrous threads, usually single but often double, the twin -- filaments held together by an envelope of gum. More or less transparent, without definite structure. k. **Wild Silk** -- Similar to cultivated silk but broader and less regular in outline. Marked by very fine longitudinal striations with infrequent diagonal cross -- markings. l. **Artificial Silk** -- Cylindrical, lustrous, appearing like a glass rod. Microchemical reactions, dissolved rapidly by half saturated chromic acid; not colored by Millon's reagent as in case of true silk. m. **Wool** -- Easily distinguished by presence of flattened, over lapping epidermal scales not found on silk or any of the vegetable fibers. Fiber many -- celled, cylindrical; shaft composed of three layers; central core or medulla (seldom seen), cortex and scaly cuticle. **4.Chemical Analysis of Fibers** -- If the sample submitted for analysis is fairly large, such as a piece of cloth or a number or large threads, it is suggested that a chemical analysis be made to supplement the microscopic examination and confirm the results obtained form that procedure. a. **Staining Test** -- The fiber is stained with picric acid, Millon's reagent, stannic chloride or iodine solution. -- ------------- Dyed Dyed Unchanged Brown Brown No reaction Black -- ------------- n. **Dissolution Test** -- If the fiber is white or light colored it is treated with the following chemicals. If dyed, the fiber is first decolorized by boiling in ether 1% hydrochloric acid, acetic acid or dilute potassium hydroxide. **Reagents:** 1. 10% sodium hydroxide 2. 5% oxalic acid 3. Half saturated oxalic acid 4. Concentrated sulfuric acid 5. Conc. and dilute Ammonium hydroxide 6. Concentrated nitric acid ### Results: 1. 10% NaOH + wool Dissolved 2. 10% NaOH + cultivated silk Dissolved 3. 10% NaOH + cotton linen, wild silk, cellulose silk Undissolved ### Chapter VI Glass is important as physical evidence because it breaks and pieces are scattered at the crime scene and on the suspect. It is a common type of thing carried away evidence in and burglary and vehicle hit and run cases. The evidence maybe fragments of a headlight leads found at the scene of a hit and run accident, window glass from the scene of robbery, or glass through which a bullet was fired. **Glass** -- This refers to a supercooled liquid which possesses high viscosity and rigidity. It is a non -- crystalline inorganic substance. ### Composition of Glass For commercial use silica is the most important oxide. It is the base of commercial glasses. It is made of silica sand and other metallic oxides. Oxide is for fluxing, durability and reduction of viscosity. Glass, like window and plate which are made in mass production is fairly uniform in composition. This may contain incidental impurities and the presence of these substances is invaluable for the identification and comparison of glass by spectrographic analysis. Gas has also presence of trace elements which may be sufficient to establish or negate the fact of a common source for two samples of glass. ### Common Oxides used in Glass Manufacture 1. Silica (SiO~2~) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- base of commercial glass 2. Soda (Na~2~O) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- acts as flux for silica 3. Lime (CaO) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- gives the glass chemical durability which it otherwise lack because of the water -- 4. Magnesis (MgO) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- present as impurity or substitute for CaO 5. Alumina (Al~2~O~2~) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- gives the glass greater chemical durability lower coefficient of expansion, and greater 6. Potash (KO) \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-- for chemical durability and resistance to devitrification ### Analysis of Glass ### Test/Analysis for Glass 1. Spectrographic Test 2. X -- ray Diffraction Test 3. Physical Properties Examination 4. Ultraviolet Properties Examination 5. Polish Marks Test ### Discussion of Test 1. **Spectrographic Test** -- an instrumental method of analysis which determines the presence of trace elements. Shows the constituent elements of glass. It will not give sufficient information to establish is the origin of the samples examined. A rapid examination and an adequate method for glass analysis since it requires only a small amount of sample. In the absence of trace elements it may be difficult to determine whether two samples of common type of glass are identical. If similar trace elements are found of both samples it is obvious they come from the source. 2. **X -- ray Diffraction Test** -- not as effective as the spectrographic analysis. It determines the type of pattern of glass. The type of pattern depends upon the composition of glass. 3. **Physical Properties Examination** -- the most sensitive method of determining differences of composition in glass samples and depends upon the study of the physical properties of glass. Properties like specific gravity and density, refractive index. Density and refractive index can be measured with great accuracy. Density or specific gravity is an especially important physical property from the viewpoint of the forensic chemist. ### Method of Measuring Density of Glass ### Method of Measuring the Refractive Index of Glass 4. **Ultraviolet Light Examination** -- determines the differences in the appearance of the fluorescent thus indication of physical and chemical differences. 5. **Polish Marks** -- optical glass and other fine glasswares are usually polished. In the polishing of glass fine marks are often left on the surface which can sometimes served as a basis of comparison. ### Procedure for the Determination of Fine Marks ### Glass as Evidence of Crime ### 1. Automobile glass in case of hit and run 2. Broken windows cause by pressure, blow or bullet in case of robbery. 3. Broken bottles, drinking glasses, spectacles found at the scene of an assault or other crimes of violence, which would suggest examination of the soles and heels of a suspect for imbedded glass fragments. ### Analysis of Glass from Vehicles Hit and run accidents represent a good percentage of crimes. In automobile or any vehicle for that matter discovered in which fragments of the lens can be found, a comparison maybe made with the fragments found at the scene of accident employing the methods of analysis for glass. ### Analysis of Broken Windows Examination of window fragments in robbery cases is important when there is a question of "as to whether the glass was broken from the outside or inside." Since our penal law specifically provides the mode of entrance before a crime may be classified as robbery, this particular kind of examination becomes very important. The general procedure to determine whether the glass was broken from the outside or inside or to determine the side from which a pane of glass was broken is to collect and piece together as much of the glass as possible in order to study the patterns of cracks and to be able to orient the pieces in their original position ### Broken Window Caused by Bullet Holes Generally it maybe said that the hole produced by a bullet of a strong charge has the sharpest edges; but if a bullet has been fired from very long distance and has come to have a low speed it will break the pane in the same manner as will a stone. A shot from a very short distance will produce the same result the pressure of the powder gas itself will smash the glass. It is easy to determine the direction from which the shot was fired. 1. On one side of the hole numerous small flakes of glass will be found to have been blown away giving the hole appearance of a volcano crater. Such appearance indicates that the bullet was fired from the opposite direction of the hole from which the flakes are missing. 2. If the shot was fired perpendicular to the windowpane the flake marks are evenly distributed around the hole. 3. If the shot was fired at an angle from the right, the left side will suffer more flaking than from the right. 4. Excessive flaking on the right side of a windowpane would indicate a shot fired at angle from the left. (The direction is taken from the person shooting) ### Broken Window Caused by Fist or Stone ### Chapter VII Traces left by a criminal in the form of foot impression, tool impression and tire impression in cases like theft, robbery, etc. will be studied in this chapter. The evidential value of an impression made by shoe, hand, tool or other articles is based in the theory that no two physical objects are alike and hence that impressions made by such object often is marked by uniquely identifying characteristics. A given impression can only be produced by one object. **Impression** -- a strong mark produced by pressure that goes below the surface. A stamp, form or figure resulting from physical contact. It causes damage to object. **Imprint** -- weak mark made by pressure that stays on the surface. In scientific criminal investigation the problem of reproducing the faithful representation of an object is of great evidential value. In many cases reliance has been placed on photographic method. In cases involving footprints, tool marks, tooth impressions, photographic representation may not serve the purpose. Using a mold called moulage can only make a faithful reproduction of these objects. **Moulage** -- a faithful reproduction of an impression with the use of casting materials. It is admitted that moulage cannot reproduce all characteristics of the object under all circumstances but whatever is mission in a moulage it can be supplied by the photograph. **Casting Material** -- any material which can be changed from a plastic or liquid state to the solid condition. **Hastening** -- add one half teaspoonful of table salt to the plaster. **Retarding** -- add one part of saturated solution of borax to ten parts of water to be used in making the plaster. One teaspoonful of sugar may also be used. **Hardening** -- to give a dried cast greater durability it can be placed in saturated solution of sodium bicarbonate and allow to remain in the solution for sometime. It is then removed and dried. **Drawback of Plaster of Paris** -- Poor mechanical strength. The fluid plastic flows into all the interstices of the mark but when the cast is removed from the mark the finer details have a tendency to break off ### Other Casting Materials: 1. **Wood\'s Metal** -- used for small impressions as tooth impression, tool impression. It is a variety of solder with melting 60o To 70°C. It is made of B -- 50%, Pb -- 25%, Sn -- 12.5% and Cd -- 12.5%. 2. **Plastic Material** -- like plasticine and dental composition. Used for small impression. Dental composition is the best casting material for making the cast of tool marks **Drawback** -- distorts when remove from the impression since plastic and never did and does not flow to the very interstices of the impressions. 3. **Negocoll** -- used for human body as cast of hand or face. It is rubbery gelatinous consisting material consisting of colloidal magnesium soap. It is rubbery 4. **Celerit** -- brown substance used for backing and strengthening the hominid. **Cast of Human Body** -- It is sometimes required to make a cast of a human hand or face. It is important that the temperature of the negative material should be below 110 F (43.3 C). A temperature higher than this will be uncomfortable if not injurious to the subject. ### Characteristics of a Good Casting Material: 1. It must be readily fluid or plastic when applied -- so that it can penetrate into minute depressions or cracks on the impression. Fluid materials are more satisfactory than plastic materials in this respect since even the most plastic material does not enter into the crevices of all the minute depression. 2. Must harden rapidly to a rigid mass -- so that no deformation of the cast takes place when it is being removed from the impression. Rapid hardening is desirable as the time factor is often of importance. 3. Must not be deformable nor shrinks -- so that if measurements are to made from the cast, it can retain exactly its size and shape. 4. Must be tough -- so that the minute lines and ridges in the impression do not break or disintegrate, so that it will stand the wear and tear it will receive during examination. 5. Must be easy to apply -- since casts have to taken under all kinds of difficult circumstances, it can readily be seen that the simpler the method the better the result. 6. Must not have the tendency to adhere to the impression. 7. Should have fine, even composition and surface -- the grain of the surface must be considerably smaller than the smallest detail it is desired to show in the cast otherwise this detail is lost in the grain. 8. Should not injure the impression. 9. Should be easily obtainable. 10. Should be cheap. (a)Shoe impressions in soil. Shoeprint examiners have difficulty analyzing low contrast photographs such as the one on the left. The shoeprint on the right has been sprayed with colored paint to increase contrast, which produces a more detailed photograph (b) Shoeprint cast in dental stone. \(a) Shoeprint collected using electrostatic device (b) Shoeprint collected using a gelatin filter ### Tool Impressions 1. Those produced by such instruments like axe, hammer, pliers and cutters which touch the area only once in producing the impression. a. **Compression Marks** -- produced by a single application of the tool in one area of contact. Example is the impression of a single blow of a hammer. b. **Friction Marks** -- these are series of scratches or striations produced by pushing a tool across the surface such as those produced cutters, axe and jimmy. 2. Those produced by such instruments like saw or file that is applied in repeated strokes over the same area. It is hard to identify since one -- mark overlaps the other. ### Examination of Tool Impression Examination of tool impression is done by comparative examination the purpose of which is to determine or to show that the particular tool made impression in question. ### Chapter VIII In criminal investigation, the branch of science known as metallurgy will in most instances be of great help in the solution of baffling problems involving pieces of metal or metal articles. Robbery, Arson, Murder, Kidnapping, Hit and Run, counterfeiting are examples of this investigation work. **Metallurgy** -- the art of extracting and working on metals by the application of chemical and physical knowledge. **Metallography** -- branch of metallurgy that involves the study of the microstructures of metals and alloys. All metals are composed of minute grains or crystals, under the naked eye and when viewed from a distance a metal appears to be homogeneous but when viewed under a metallography microscope the crystal structure is visible. These crystals of the metal are tightly packed. Application of Metallurgy in Criminal Investigation 1. Robbery 2. Theft 3. Hit and run 4. Bomb and explosion 5. Nail examination 6. Counterfeit coins 7. Restoration of tampered serial number ### Counterfeit Coins ### Two Kinds of Counterfeit Coins: 1. Cast coins -- coins made in molds. 2. Struck coins -- coins made by striking or stamping method. ### How are Counterfeit Coins Made 1. Cast Coins -- An impression of genuine coin is taken by use of Plaster of Paris, clay or bronze. The plaster molds bearing the image of a good coin are filled within a low temperature alloy made with lead or tin. Sand molds are used for high temperature metals such as copper or silver alloys. Cast coins have poor imitation. It can be easily detected. The surface is usually pitted and uneven. The edge of letterings and designs are rounded instead of sharp. 2. Struck Coins -- Made by striking or stamping method. Consists of making an impression of a coin on a metal blank by pressure. Stamping is done by way of steel dies. Often well executed. Its detection is not easy since weight, specific gravity, composition may all be good. Careful comparison of smaller details of the design with those of the genuine should be made. ### Tampered Serial Numbers Tampered serial numbers are restored by the application of etching liquid. Etching fluid is a fluid used to restore tampered serial numbers. Choice of etching depends on the structure of the metal bearing the original numbers. ### Etching Fluids 1. For cast iron and cast steel -- 10% sulfuric acid and potassium dichromate. 2. For wrought iron and forged iron -- solution no. 1 (hydrochloric acid is 80 ml, water is 60 ml, cupric chloride is 2.9 grams and alcohol is 50 ml) Solution no. 2 (15% nitric acid) 3. For aluminum -- glycerin is 30 ml, nitric acid is 10 ml, and hydrofluoric acid is 20 ml. 4. For lead -- 3 parts glacial acetic acid and one part water. 5. For stainless steel -- dilute sulfuric acid or 10% hydrochloric acid in alcohol. 6. For copper, brass, silver and other copper alloy -- ferric chloride -- 19 grams, hydrochloric acid -- 6 ml, and water -- 100 ml. 7. For tin -- 10% hydrochloric acid. 8. For zinc -- 10% sodium hydroxide. 9. For silver -- concentrated nitric acid. 10. For gold and platinum -- aqua regia (3 parts hydrochloric acid and one part nitric acid) 11. For wood -- subject to a jet of steam. overlooked by most investigators, probably because it is such a common place substance and is more or less taken for granted. Very few persons have realized upon which they stand may have a different composition from the soil a few yards away. Researchers have shown that soil are greatly diversified and vary considerably over the surface of the earth not only from widely separated points but also from points quite close together. This is expected because soil represents not only original earthy constituents derived from the parent rock of the natural forces and the activities of living organism over millennia. Soil varies rapidly with depth. The admixture of soil from below the surface with surface soil is taking place constantly in excavating for pipes, paving and in agricultural operations. Surface variations may arise, therefore due to admixture with surface soil of the same region. Addition for fertilizer and soil conditioning material and human, animal, and plant waste would cause further variations of local nature. In view of this variation in compositions soil can only be used as circumstantial evidence in crimes of violence. There is the remote possibility that another soil from some part of the country would be identical, although this has never been found to happen. **Petrography** -- is the branch of geology that deals with the systematic classification and identification of rocks, rock forming minerals and soils. Also includes study of dust, dirt, safe insulation, ceramics and other such materials both natural and artificial. Soil means different things to different people. A farmer plants crops in it. An engineer builds with it. A miner takes mineral from it. Criminalist regards soil as the top layer of the earth. It may include any substance on the earth that may stick a person\'s clothing or shoes. ### Types of Soil 1. **Alluvial Soil** -- formed from soil particles that were washed, blown, or moved by gravity to the lowlands. Earth, sand, gravel, etc. are deposited by moving water and wind. Its particles may be derived from an almost infinite number of sources, and since the action of water and wind would in few cases be identical over long periods of time in different spots, great variations in composition would be expected. 2. **Colluvial Soil** -- formed from the decomposition of igneous, metamorphic and sedimentary rocks, the decomposed particles moved by gravity. Soil in which some movement and intermingling of parts has occurred would be expected to be less variable. 3. **Sedentary Soil** -- inactive, not migratory soil. ### Collection and Submission of Soil 1. Soil usually in form of mud is usually recovered from shoes, slippers, clothes, tires, tools and furniture. 2. If found on the above the soil should remain in place and the whole submitted to the laboratory 3. Should be wrapped in a clean paper or filter paper and placed in a box. 4. Known soil samples should be taken at different places around the point or reference. ### Constituents of Soil The basic component of soil originates primarily from mechanical and chemical decomposition of igneous, metamorphic and sedimentary rocks. Rocks are almost infinite variable in composition containing usually many different minerals. **Metamorphic Rock** -- has undergone changed in structure, texture through pressure, heat and chemical reaction. Like limestone into marble. ### Constituents of Soil 1. **Primary minerals** -- includes undecomposed rock fragments ranging from stone down through pebbles, sand and silt. ### Important Minerals a. **Quartz** -- a form of silica. Crystalline mineral usually colorless and transparent. Also called quartz sand. It originates primarily from igneous rock but much of the soil quartz is contributed directly by metamorphic and sedimentary rock. A common mineral. An almost universal component of soil b. **Calcite (Limestone -- CaCO)** -- white reacts with acid with evolution of carbon dioxide. Occurs widely particularly in calcareous soil. c. **Feldspar (Silicate of Aluminum or Sodium, or Barium, Calcium, Potassium)** -- their composition gives rise to clay along with more or less soluble salts of the metals named. d. **Dolomite Limestone** -- white mineral obtained from sedimentary rock. Similar to Limestone. e. **Mica** -- a mineral that crystalline in thin, flexible layers, resistant to heat. f. Other primary minerals: Gypsum, Talc, Kaolinite, Limonite, Magnetite. 2. **Clay minerals** -- a product of decomposition of primary minerals. Found nearly all soils and is the major constituent of most heavy soil. It imparts to soil cohesiveness and plasticity and becomes hard and adherent on heating. Pure clay is considered by criminologist to be hydrated aluminum silicate. The color of clay soil varies from white through red, yellow, green, or blue depending on the nature of the admixed impurities. 3. **Organic constituents** -- one of the most variable of all soil constituents and are of peculiar importance in the identification of soil. Agricultural land is likely to be particularly rich in organic constituents both from growth occurring on the land and from added materials such as manure, peat and cover crops. Richest of all are the peat and muck soils which have been formed primarily from the constant decay of organic matter and contain only a small amount of residual mineral deposits mostly by flooding. Humus constituents are the most important black coloring matter of soil. It alters texture markedly, making clay soil less cohesive and sandy soil more so. ### Analysis of Soil The identification of soil is never necessary that all constituents be identified as such or that they are separated. Any method which quantitatively distinguishes particles of characteristics appearance of properties will be successful in providing identity or non -- identity depending on whether the distribution found in two soils are the same or different. There are several methods of petrographic analysis that are being used in the laboratories to establish the identity of two or more samples of soils. There is no procedure which is specially recommended. In the crime laboratory the use of Density Gradient Apparatus is utilized. A simple procedure of determining the identity or non -- identity of soil samples based on the density distribution. The procedure is rapid, requiring a few hours of completion. Consists of simple apparatus and is indeed so sensitive to small changes in composition. ### Other Methods of Analysis for Soil 1. X -- ray diffraction 2. Spectrographic Analysis 3. Thermal Analysis ### Application of Soil Analysis to Scientific Crime Detection The value of soils as evidence depends wholly upon the fact that soils differ in various characteristics over the surface of the earth. This difference makes it possible to establish the identity where about of a person under investigation. ### Dust and Dirt Dust and dirt has been described as \"matter in the wrong place". The study such piece of evidence may often provide the investigator with clues as to the occupation of previous where about of a person under investigation. **Dust** -- matter which is dry and in finely divided form. **Mud** -- dust mixed with water. ### Composition of Dust Whatever is the origin of dust and wherever it is found it always contain substances derived from substances of plant and animal origin and substances of mineral origin. ### Classification of Dust source. 1. **Dust Deposited from the Air** -- extremely fine dust particles present in the air everywhere. More abundant in thickly populated and industrial regions. Settle very slowly and ultimately deposited on an exposed surface. Its value in crime detection is insignificant. 2. **Road and Footpath Dust** -- produced by the wear and tear of the road surface by vehicular and pedestrian traffic together with particles of soil carried by the wind or rain from adjoining regions. 3. **Industrial Dust** -- industries like cement, button, powdered gypsum and plaster of paris factories, flour milling paint pigments, involves industrial processes impart a pronounce local character to the dust on the neighboring roads and buildings. 4. **Occupational Dust** -- some of the finely powdered material may be found on the clothing and footwear of employees engaged in such industries. Aside from this for example, bricklayer will yield brick dust, sand and lime on his clothes. Coal miner will have coal dust on his clothes. In criminal investigation the identification of the person through the articles of clothing left in the scene of crime or in a vehicle may place him in an identifiable class and thus serves to distinguish him from the great majority of other persons. Such observation does not serve to distinguish the wearer of the cloth from all other persons. ### Collection and Submission of Dust and Dirt Dust and dirt present in clothing or objects that can readily transport should be left in situ. The whole article is packed in a clean box with proper protection and shipped to the laboratory. If the object is immovable or too big to submit as a specimen like sofa, piano, dresser, the specimen may be removed by the use of a vacuum cleaner with paper bags used in the dust sack to collect the dirt. If a vacuum cleaner is not available the clothes may be placed in a clean paper bag and beaten to remove dust and dirt. ### Analysis of Dust and Dirt The identification of dust/dirt is usually made for the purpose of determining the occupation of the suspect or finding evidence that maybe similar o identical with that found at the scene of crime. Quantitative examination is rarely necessary but qualitative test should be made for metals present. If the sample is very small, microchemical test or s spectrographic analysis maybe employed. If the amount of specimen is sufficient following is employed. 1. Examine the sample under the ultraviolet light. 2. Treat a small quantity with a drop of water on a spot plate. a. Observe color of aqueous drop with hand lens b. Note the proportion of the solid matter which remains in suspension and proportion which settles rapidly c. Reaction with litmus settles rapidly 3. Treat a small quantity with a drop of 0.1 N Hydrochloric Acid d. Note the evolution of gas e. Note formation of precipitate f. Note change in color g. Note materials dissolved by acid 4. Treat a small quantity with Ethanol h. Note color of alcohol drop i. Note difference between the color of an aqueous solution in process 2 and that in color solution j. Note other changes In the investigation of crimes involving the use of firearms, three most important problems may arise. The first and probably of primary importance is the problem of determining whether or not person has fired a gun with bare hands within a pertinent period of time. The other is the means of determining the probable gunshot range e.i., the distance the firearm held from the body of the victim at the time of discharged. A third problem may come up when the time of the firing of the from the body of the victim at the gun becomes an issue. ### Two kinds of Gunpowder 1. **Black Powder** -- because of its inherent defects modern ammunition plants abandoned the use of this. 2. **Smokeless Powder** -- is the most widely used propellant. It can either be single base propellant or double propellant. **Black Powder** -- possibly the oldest known explosive. It is consists of an intimate mixture of charcoal -- 15%, sulfur -- 10% and potassium or sodium nitrate 75%. When exploded in open space the following reaction occurs: This reaction holds true if the composition of the powder is uniform, pure and no either side reactions take place. Slight difference in composition cannot be avoided as well as side reactions cannot be controlled. **Smokeless Powder** -- the most widely used propellant. It is consists of Cellulose Nitrate or Glyceryl Nitrate combined with Cellulose Nitrate and some stabilizers. Among the stabilizers used are Nitrates, Bichromates and Oxalates. Some of the organic stabilizers are Nitrobenzene, Graphite and Vaseline. Stabilizers are added to reduce side reactions. These combine with the products of decomposition and may have a negative or positive catalytic effect. When exploded the following reactions occur: ### Possible Locations of Nitrates when Black Powder and Smokeless Powder Explode It will be noticed that nitrates are present in both gunpowder so that one will expect to find nitrates (NO) in the following: 1. Residue or the barrel of the gun 2. In or around the wound 3. On the clothing of the person fired upon at close range 4. On the exposed surface of the hand of the person firing the gun ### Factors That Affect the Presence and Amount of Gunpowder Residues ### a. Type and Caliber of the Ammunition -- different types of ammunition fired in the same weapon and from the same distance may give different pattern. b. Length of the Barrel of the Gun -- a weapon with 2 inches barrel will deposit residues over a larger area than a weapon having a five inches barrel even though they are fired at the same distance and with the same type of ammunition. c. Distance of the Muzzle of the Gun from the Target. d. Humidity -- affects the speed with which powder burns. Powder having lesser amount of moisture will burn more rapidly and completely within a given time yielding greater amount of residue. e. Wind Velocity and Direction -- in high winds the residue will be blown in the directions of the wind yielding a scattered pattern. f. Direction of Firing -- firing vertically, slightly greater than firing horizontally from the same distance. Powder residues have weight. When gun is fired downward o vertically all of the residence will fall on the target, but when fired horizontally some of the residues are likely to fall short of the target. I. ### Determination of Whether or not a Person Fired a Gun with his Bared Hands The burned residues are partially burned particles may escape around the breech of the gun and implanted on the exposed surface of the hand firing the gun and the presence of this particles serves as a basis for the diphenylamine -- paraffin test (DPA -- Paraffin Test). ### Theory upon which the Diphenylamine Paraffin Test is Based At the instance of discharge there is a certain amount of gases and mixture of burned residues and partially burned particles that escape from the breech of the gun. These particles strike the exposed surface of the hand holding the weapon and became implanted into the sin. ### Diphenylamine Paraffin Test or Dermal Nitrate Test or Lunge ### Procedure: a. Paraffin Test -- the taking of the cast to extract the nitrates embedded or implanted in the skin. b. Diphenylamine Test -- the chemical aspect of the test. It determines the presence and distribution of nitrates. **Reagent:** Diphenylamine reagent (0.5 gram diphenylamine crystals dissolved in 100 ml of sulfuric acid and 20 ml of water). **Visible Result:** Deep blue specks that develop when nitrates come in contact with the diphenylamine reagent. ### Limitation of the Diphenylamine -- Paraffin Test: 1. The test is not specific for nitrates since the role of nitrate is simply oxidizing agent. The test cannot determine the source of nitrate. 2. There are other substances which contain nitrate oxidizing agents that are not in the ordinary course of life like fertilizers, explosives, tobacco, firecrackers, urine, cosmetics and detergents. 3. In general persons do not have nitrates or other oxidants on their hands as a matter of common occurrence. 4. Hands contaminated with nitrates from other sources other than gunpowder or any oxidant one will expect to find either a smear blue color or conglomeration of blue specks located at the different places of the hand both dorsal and palmar aspects. ### Possibilities That a Person may be Found Positive for Nitrates even if he did not Actually Fire a Gun 1. It is possible that the gunpowder particles may have been blown on the hand directly from the barrel of the gun being fired by another person. 2. An attempt to shield the body by raising the hand would in some instances result in the implantation of powder particles on the hand of a person close to one firing a gun. ### Possibilities That a Person may be Found Negative for Nitrates even if he did Actually Fired a Gun 1. Direction of the wind 2. Wind velocity 3. Excessive precipitation 4. Use of gloves 5. Knowledge of chemicals that will remove the nitrates The leakage of powder is apt to occur when the gun fired is old weapon where the breech mechanism is no longer tightly titled and when the gun used is of the revolver type. In cases involving shooting incidents where paraffin test is required, the person suspected to have fired a gun should be subjected to diphenylamine -- paraffin test immediately and in no case should it be postponed seventy -- two (72) hours after shooting. It is possible to detect nitrates as late as three days even though the hands have been washed. In the Philippines the period is reduced to two days only due to excessive perspiration. ### Determination of the Probable Gunshot Range or the Distance the Firearm was held from the body of the Victim at the Time of Discharged ### How to Collect, Preserve and Pack Clothing Clothing removed from the victim should be cautiously and carefully handled to prevent powder residues for becoming dislodged. c. A large area as possible surrounding the gunshot hole should be made available for the test. If the condition and appearance of the wound point to a contact shot at all of the clothing in the path of the bullet should be collected and submitted for examination. d. Do not wad the specimen or pack it loosely for shipment. Secure the areas to be tested between two layers of heavy cardboard fastened together tightly prevent the specimen from becoming jostled about in transit. e. Each specimen should be wrapped separately f. Clothing heavily smeared with blood should be dried thoroughly before packing. If wet, they may become mildewed or stick together in such a way that they will be unsuitable for the test. The letter transmittal should contain all information as to existing circumstances and conditions known to the investigator which may become helpful in making the test. ### How to Determine the Probable Gunshot Range The clothing is examined microscopically for possible powder residue, singeing. burning, smudging and powder tattooing. a. Singeing -- slight burning b. Smudging -- blackening of area around the bullet hole c. Tattooing -- individual species of nitrates around the bullet hole visible to the naked eye. It is a black coarsely peppered pattern. ### Three Zones of Distances from which a Firearm was Discharged 1. Those in which the muzzle of the gun was held directly in contact with the body or practically so. 2. Those in which the muzzle of the gun was held 2 inches to 36 inches away. 3. Those in which the muzzle of the gun was held beyond 36 inches 1. Gaping hole where fabric is badly torn; 2. Smudging; 3. Singeing of the fibers at the entrance; 4. And tattooing. Presence of partially burned powdered residues around the entrance hole that may be embedded in the fabric. This could be present originally but may have become dislodged by rough handling of the specimen or may have been blown into the wound or may have been wasted by bleeding. **Held from 2 inches to 8 inches (maximum):** The smoke and soot from the burned powder will be deposited around the hole of entrance producing a dirty grimy appearance (covered with soot, dirt adhering or embedded on the surface). More pronounced when the ammunition used contains black powder. Smudging around the perforation will be found to diminish in size as the muzzle of the gun is held a distance of eight inches all the blackening around the hole completely disappear and few individual specks of tattooing will be visible with the naked eye. The size of the smudge depends upon the caliber of the gun, type of powder used, length of the barrel, distance of the muzzle of the gun was held from the body. The size of the area of the powder tattooing will also depend on the caliber, powder charge and distance of firing. A close observation of the area surrounding the gunshot hole will show that the granule mark or powder tattooing is not distributed evenly around the hole. A greater bulk of them is deposited on one side of the hole. This is due to the fact that when cartridge is fired, the bullet leaves the muzzle of the gun first, followed by the expanding gases and the burning powder. This cause the gun to kick, throwing the muzzle off the target and this kick is always towards the direction of the sights. The kick of the gun causes the smudge and powder tattooing to be deposited more on one side of the hole than on the other, and the side of the greatest deposit indicates the side on which the sights of the gun was mounted. This observation is helpful in determining whether the wound was due to suicide or murder. If the gun was discharged from a position in which the victim could not easily have held himself, intends to indicate a murder. The size of the area of powder tattooing will also depend on the caliber, powder charge and the distance of firing. **Held from 8 inches to 36 inches:** Tattooing is visible. The partially burned and unburned powder particles will be driven into the surface around the gunshot hole producing a black coarsely peppered pattern called tattooing. ### Chemical Test for Gunpowder Residues There are two methods of determining the presence of gunpowder residues around the gunshot hole namely: 1. A method patterned after the Diphenylamine -- Paraffin Test. **Procedure:** Coat a piece of clean gauze with a sufficient amount of parallax to produce a layer of about 1/8 inch. Press this layer of paraffin while still warm against the area to be examined. 2. Walker\'s Test -- This test is used if the powder particles are deeply embedded. It is based on the conversion of nitrates to a dye. ### Procedure: 1. Immerse the photographic paper in a new hypo solution for 15 minutes so that all the silver salts are dissolved. 2. The paper is washed in running water for one hour. 3. The desensitized paper is immerse in a 5 to 10% aqueous solution of C -- acid (2 -- Naphthylamine -- 4, 8 -- disulfonic acid) for ten minutes and then dry. 4. Lay a clean towel on the table and the prepared C -- paper is laid face up on this. 5. The fabric to be examined is then laid face -- down on the photographic paper. 6. Place thin dry towel of cotton cloth moistened with 20 to 25% acetic acid. 7. Place another layer of dry towel. 8. Press the illuminated arrangement with warm electric iron for ten minutes. **Visible Result:** A number of orange red spots are imprinted on the photographic paper. ### Gunshot Range of Weapons Other Than Pistol and Revolver 1. **Rifle** -- A weapon on high velocity projectile: Gunshot range is difficult to estimate due to high velocity of the projectile and the wide variation produced on the wound of entrance. The tissue through which the bullet passed is usually bruised in varying degree. As a general rule the size of the wound closely appreciate the size of the bullet. 2. **Shotgun or Sporting Gun** -- The projectile is a collection of small shot consisting of lead pellets that vary in size with types of cartridge. a. The pellets disperse soon after their exit from the barrel and the dispersion increases with the range. b. The shot discharged from the average cylinder sporting gun will cluster together and not separate to any appreciable extent until the cluster has travelled approximately 3 to 4 feet from the muzzle of the weapon. c. If a shot is fired closed to the body up to a few inches the shot enters as a mass and the liberated gas and flame lacerate the tissue around the hole and show evidence of burning, carbon deposit and powder tattooing. d. When fired from 3 feet from the body a more or less irregular circular wound about 1 ½ inches to 2 inches in diameter will be produced. There will be scorching, carbon deposit and powder tattooing. e. At a range over a yard and up to about 3 yards evidence of burning disappears and probably only faint tattooing will be found f. Beyond a yard the entering shot produces an irregular wound and as a result of commencing dispersion of the shots individual pellet holes may be detected. III. ### Determination of the Probable Time the Gun has been Fired In the determination of the approximate time of last discharge the specimen firearm is needed in the examination. At the Crime Laboratory, if the gun is examined immediately after the shooting the chemistry rely more on the odor of the barrel. A characteristic smell will be present that decreases in intensity with lapse of time, as smell of hydrogen sulfide. If the gun is examined later presence of nitrates, nitrites, rust soot and metallic fragments are determined. **Procedure** -- The barrel is swabbed with cotton with the aid of a barbecue stick and the presence of the following is determined microscopically and chemically. 1. Soot -- a black substance that is formed by combustion rises in fine particles and adheres to the side of the barrel conveying the smoke. 2. Metallic Fragment 3. Rust -- formation of rust inside the barrel after the gun has been fired is good indication for the determination of the approximate time the gun has been fired. If a gun has been fired, Iron salts are formed and are found inside the barrel. This iron salts are soon oxidized resulting in the formation of rust. 4. Nitrite -- presence of nitrite (NO) is determined by the addition of diphenylamine reagent. If the color becomes blue, nitrites are present and we may say that the firearm could have been fired recently. 5. Nitrate -- presence of nitrates (NO) is determined by the addition of diphenylamine reagent. If the color becomes yellow green, nitrates are present and we may say that the forearm could have been fired but not recently. ### Explosives The Crime Laboratory does not only examine explosive confiscated from some lawless elements of society that they utilize for criminal purposes, but also explosives used in illegal fishing. **Explosive** -- is any substance that may cause an explosion by its sudden decomposition or combustion. A material either a pure single substance or mixture of substances which is capable of producing an explosion by its own energy. When exploded always accompanied with the liberation of heat and almost with the formation of gas. ### Explosives Can Be Classified as follows: 1. From the viewpoint of chemical composition 2. With respect to functioning characteristics ### Classification of Explosives from the Viewpoint of Chemical Composition A. **Inorganic Compound** Examples: Lead Azide Ph (N) Ammonium nitrate NH NO ### Organic Compound Examples: Trinitrotoluene (TNT); picric acid (trinitrophenol nitrocellulose; mercury fulminate Hg(ONC) C. **Mixture of oxidizable materials and oxidizing agents that is no explosives separately** Examples: Black Powder -- used today mainly as igniter for nitrocellulose gun propellants and also in pyrotechnics. ### Classification of Explosives with Respect to Functioning Characteristics 1. **Propellants or Low Explosives** -- are combustible materials containing within themselves all oxygen needed for their combustion which burn but do not explode and function by producing gas which produces explosion. 2. **Primary Explosives or Indicators** -- explode or detonate when they are heated or subjected to shock. They do not burn. Sometimes they do not even contain the elements necessary for combustion. The materials themselves explode and the explosion results whether they are confined or not. 3. **High Explosives** -- explode under the influence of the shock of the explosion of a primary explosive. They do not function by burning, in fact not all of them can be ignited by a flame and in small amount generally burn tranquilly and can be extinguished easily. If heated to a high temperature by external heat of by their own combustion, they sometimes explode. 1. **Ammonium Nitrate (AN)** -- most readily available and cheapest salt of nitric acid. White compound used as a solid oxidizer in explosive mixture. 2. **Dynamite** -- made by mixing nitroglycerine with powdered clay or sawdust. 3. **TNT -- or Trinitrotoluene** -- the most widely used explosive. Used mostly for military explosive. A safe explosive, it will burn but does not explode set on fire. 4. **Nitroglycerine (NG)** -- widely used in industrial explosive. Has been the main component in many dynamites. It is a mixture of Nitric Acid, Sulfuric Acid and Glycerine. Oily liquid that is very dangerous because the slightest shake will cause it to explode. 5. **Plastic Explosive** -- a military explosive that looks like ordinary putty or molding clay. Military explosives are chiefly solids or mixtures formulated as to be solid at normal temperature of use. 6. **Picric Acid** -- also called trinitrophenol. ### Other Explosives: 1. **C -- 4** -- often referred to as a plastic explosive. White and dough like in consistency. It is commonly encountered of the RDX based explosive. 2. **RDX -- (1,3,5 -- trinitro --1,3,5 triazacyclophexane)** -- Also called hexagon or cyclonite, cyclotrimethylenetrinitramine. A plastic explosive. Most important military explosives used today. 3. **Chloroacetophenone (CN)** -- the principal constituent in the filter used in tear gas solutions. Commonly used tear gas. 4. ### Fire Bombs a. **Molotov Cocktail** -- is an incendiary device, not a bomb. Easily constructed of the most common materials. Consists of frangible container, like glass bottle filled with gasoline or any inflammable mixture and having a piece of absorbent cloth for a wick or fuse. To function the container is turned upside down and the wick absorbs the flammable mixture, the wick lighted and thrown. On impact the bottle breaks scattering the flammable mixture which is ignited by the burning wick. b. **Modern Molotov** -- consists of 2/3 and 1/3 gas and sulfuric acid respectively. A blotter which has been saturated in potassium chlorate and sugar is wrapped and secured to the bottle. A snowball consists of potassium chlorate and sugar mixture embedded in a wax mold using a length of safety fuse for an ignitor. c. ### Acids mixed with the gasoline and wicks attached to the outer bottle d. **Mixture of alcohol and gasoline using a chrome oxide strip taped to the bottle** which when thrown will burst violently 5. ### Demolition and Fragmentation Explosives 1. Composition A -- mixture of RDX and beeswax, Semi plastic in nature. 2. Composition B -- is a mixture of RDX, TNT and beeswax. 3. Composition C -- sometimes referred to as plastic explosive, is RDX and inert plasticizer composition. 4. C -- 2 -- is RDX and explosive plasticizer. Contains no tetryl. 5. C -- 3 -- RDX and an explosive plasticizer with tetryl substituted in part of RDX. 6. C4 -- is RDX and plastic explosive composition.