Forensic Chemistry Part 2
INTRODUCTION
In the investigation of crimes involving the use of firearms, the investigating officers need to know whether a suspect has fired a gun or not and the gunshot range or the approximate distance of the firer to the victim.
The Gunpowder and the Hand
When a firearm is discharged unburned particles of the gunpowder may escape through the breech of the gun and deposited on the hands of the firer, on the clothing of the victim and some may remain in the barrel. These gunpowder residues can be detected by chemical examination.
The above picture through infrared photography shows how gunpowder residue is expelled from the muzzle of the gun (revolver) and through the cylinder in red and green color which may adhere to the hand, face, and hair including the clothing of the firer because of the forces of the gas that resist against the air and forces said residue to move backward.
This phenomenon is unknown to the firer EXCEPT for those who learn the science of firearms and its action. The tiny particles of primer and gunpowder residue through forensic analysis can be detected by the examiner and can be proven scientifically.
Concerning suspected bombings, the laboratory is requested to detect traces of explosives that may be found in the remains of parts of the bomb. Explosives like improvised and manufactured dynamite used in illegal fishing are also examined.
Description of Gunpowder and Other Explosives
There are two types of gunpowder used in the ammunition of small firearms:
Blackpowder – first invented, consist of a mixture of carbon (charcoal=15%) sulfur (10%), and potassium (sodium) nitrate is 75%); and
Smokeless – which can be either single based, consisting of nitrocellulose and nitroglycerine (glycerus nitrate) certain inorganic and organic compounds are added as stabilizers.
Types of Explosives
« Mechanical – such as those caused by expansion of gas-producing high pressure- beyond the capacity of the container (explosion of ammunition, bomb, and LPG tank).
« Atomic – resulting from atomic transformation (Atomic Bomb, Hydrogen Bomb and the like)
« Chemical – produced though the extremely rapid transformation of the unstable substance accompanied by the formation of the heat (potassium permanganate in contact with glycerin, gasoline when solidifying due to aluminum stanate)
Classifications of Explosives
The speed of the chemical reaction or detonation of the explosives determines the classification of explosives as low, initiating, or high explosive: Any substance that may cause an explosion by its sudden decomposition or combustion are known as EXPLOSIVES:
Ø Low Explosives are low burning and are used mainly as propellants, like black powder and smokeless powder.
Ø Primary or Initiating explosives are extremely sensitive to detonation by heat, shock friction, and the impact they detonate without burning, like lead oxide and mercury fulminate.
Ø High Explosives have very fast or high detonating rates, like dynamite TNT and RDX.
THE METHODS OF EXAMINATION
Whenever a person is suspected to fire a gun, it is important that such subject person be invited (if arrested as a result of his act when caught after committing a crime, must be subjected to an examination) at the crime laboratory for “PARAFFIN CASTING” to examine the presence of gunpowder nitrate within seventy-two (72) hours after the incident. Although there is still a possibility of discovering gunpowder residue on the hand after seventy-two hours, it is advised that the suspect must be recovered earlier than the said prescribed number of hours.
Why area of thumb and forefinger? See the picture below of a hand firing a gun. You will notice that the top (upper) portion of the said hand is exposed openly to the explosive gas that may come out of the gun (encircled with a red mark), hence such part must be examined properly as an indicator for firing a gun.
If other parts of the hand (middle, ring, and little finger, and palm) have blue specks and are evenly distributed, it may possibly be due to a CONTAMINANT, not a gunpowder residue.
Using the forceps hold a piece of cotton dipped into the melted paraffin wax (low melting point wax=48-60 degree centigrade (118.4-140 degree Fahrenheit) about 15 inches above the hand of the subject. NOTE: NEVER USE A CANDLE FOR THIS PURPOSE because the candle is a high melting point of wax! Allow the paraffin in cotton to drop from said position on the dorsal aspect of the hand from the wrist joint to the fingertip until it is completely covered with a thin coating of paraffin.
Make the coating even by rubbing it with cotton or melted paraffin. Place on top a thin layer of cotton for reinforcement. Cover this cotton layer with another coat of paraffin. Put a piece of paper 2×2 inches containing all the information [date, place, nature of case, time name of subject, the nature of taking the paraffin, and name of the witness] then paste this on the top of the cast.
When the cast has set, peel it gently from the hand. Wrap the cast in a clean sheet of paper to avoid contamination.
Are all hands found to have blue specks positive for gunpowder nitrates?
I have mentioned that before, that only the ‘THUMB and INDEX FINGER must be analyzed.
Note that the blue colors that appear indicate the reaction of the nitrates with Diphenylamine reagent thus nitrates from other sources like fertilizer, will give the same reaction. Other substances similar to nitrate are known as oxidizers will also react with the reagent in the same way thus, the location, distribution, and character of the specks are considered to eliminate the other possible sources of the oxidizer.
NEUTRON ACTIVATION ANALYSIS
A more specific test being employed by the better-equipped police laboratories like the FBI is neutron-activation analysis. This required access to nuclear reactors and facilitates detecting the radiation from gunpowder and gun explosion. The use of this is highly restricted because of the prohibition of developing a nuclear reactor.
CAN A GUN BE SUBJECTED ALSO TO ANALYSIS TO DETERMINE IF IT WAS FIRED?
YES! The diphenylamine reagent is also applied in cotton swabbing at the barrel, and chamber of the gun to determine if the firearm was fired, again a deep blue color resulting from the reaction of nitrates with the reagent indicated the presence of the gunpowder residue. An INDICATION that the gun had been fired.
The test kit above is a useful kit for this purpose and can also be applied in a hand aside from the gun.
THE GUNSHOT RANGE DETERMINATION
When A gun is discharged, gunpowder residue may also be deposited on the cloth or clothing of the victim. The size and density of the pattern of gunpowder residue found on clothing are the main factors considered in determining the approximate distance of the firer to the victim. As the distance to the victim increases, the size of the pattern increases while density decreases and vice versa.
DETERMINING THE DISTANCE OF THE FIRER
If the estimates are to be reliable, the actual gun used and similar type of ammunition must be tested fired on the same target under the same conditions as possible as during the commission of the crime. The following is valuable information for an analyst to understand the range determination. Examples of gunshot range determination are as follows:
Below is an actual example of Gunshot Range Residue on target:
Description of gunpowder residue will be discussed further when you took your “Forensic Medicine” including how a gunshot wound looks according to distance and the appearance of (see picture below) tattooing, singeing, and smudging.
THE EXPLOSIVE ANALYSIS
There are specific tests for each kind of explosives. In addition to techniques using chemical reagents, thin layer chromatography (TLC) and infrared spectrophotometry have resorted too. These methods are found more specific and faster.
This kit provides rapid screening for the explosive residue to verify the presence of nitrates. Due to improvements in testing techniques, the process is extremely sensitive and ideal for field or lab use. Tests have been performed with debris the size of a grain of salt —while not conclusive for the presence of explosives, it is an effective screening tool for pinpointing “hot” locations.
Handling and Disposition of Bomb
Only a qualified expert should handle bombs, therefore do not handle bombs unless qualified. Upon discovery of suspected bombs, the following steps should be taken:
Clear and secure the area. Post guards outside of the danger area.
Do not touch or move anything connected with it.
Contact the bomb disposal experts.
Notify fire and rescue squads. Medical aid should be ready.
Remove flammable materials near the area.
Shut off the power, fuel, electrical, and its services.
THE HUMAN HAIR
Remember the Locard’s Exchange Principle: there is always a cross transfer of evidence between the suspect and victim including that crime scene. He says in “EVERY CONTACT IT LEAVES A TRACE, and this is what the investigators must NOT neglect on some crimes involving physical contact between the suspect and the criminal.
In this particular topic, we would like to invite you to watch and listen to our short video entailing the different questions you might ask and wonder why “HAIR BECOMES AN IMPORTANT PIECE OF EVIDENCE in a crime. I am inviting you therefore to click the video presentation below and learn the essence of the subject matter:
You are now aware of what is hair as evidence! Be able to remember and put in your mind all your takeaways in the video presentation.
THE FIBERS AS EVIDENCE
What are your takeaways from this lesson?
It is important for a future criminologist to be good not only in thinking methodology during the investigative process where diverse evidence might have been discovered as a result of the action of the criminal but must enable all his senses to work.
Citing again the different examples mentioned in the two topics (hair and fibers), your knowledge in investigating crime is now enhanced. BE ABLE TO REMEMBER all those learning for your mid-term examination after our last presentation here.
PAPERS AND INKS
The ORIGIN of the paper may arise as a question in the course of an investigation. Discovering the source of the paper for example sometimes solves cases of anonymous letters. One of the clues to the operations of a forger is the source of his blank checks. Papers can often be identified and distinguished by means of their composition, processing, and marking. In addition, the handling of papers after manufacture may result in identifying marks. The following are the typical objectives of comparison with paper standards:
[1] To determine whether the standard is similar to the paper bearing the questioned writing. (magkaparehas ba ang pinanggalingan ng papel: Tagalog)
[2] To determine whether a sheet of paper was taken from a particular pad or tablet. For example, that matching the partially perforated edges that questioned check can show it was taken from a particular checkbook (ang kaputol ba ng papel tulad ng tseke or ticket tulad ng nasa larawan sa ibaba ay galing sa isang booklet o pad ng tseke: Tagalog).
Again by matching perforated edges, it is sometimes possible to show that the stamp on a questioned envelope was removed from another stamp or sheet of stamps found in the possession of the suspect (maari bang malaman kung ang stamp ay galing o tinanggal sa ibabaw ng isang sobre o papel: Tagalog)
[3] To show that one document was in contact with another. The shape of the blot may establish this for example, which had seeped through the questioned document and stained some of the underlying sheets of the tablet (ang pinagpatungan ay magpapakita ng bakat ng marka ng diin o tinta: Tagalog).
In a recent narcotic case, it was possible to show that the glassine envelope containing the shabu found in the addict’s possession had been removed from a stack of envelopes (ang envelop ba na nilagyan ng kontrabando ay kinuha o galing sa iisang lagayan lang) on the counter of the suspected pharmacy, which is front in selling prohibited drugs.
[4] The glue with which the lower end of the envelope was sealed in the process of manufacturing had in drying, causing the envelope to adhere to the next lower one in the stack of an envelope. On separating, the fibers of the lower envelope had been disturbed in a recognizable outline.
Standards of Comparison
Standards will be required whenever the source of paper becomes a point of interest in the investigation. It is found that forgers and writers of anonymous letters often exercise great care in selecting a suitable paper even making a special purchase to suit their needs.
The investigator may discover paper standards in the suspect’s quarters or place of business or he may be required to search for the place of purchase (ang pinakamagandang hanapan ng ebidensya ay ang quarter ng FORGER dahil doon mo matutuklasan lahat ng kanyang ginamit pati mga sample paper na kanyang pinagpraktisan, lalo na sa kanyang working table o lamesa at trash bin or basurahan: Tagalog). In the latter event, the advice of a stationery or paper manufacturer should be sought in the problem. At least five sheets should be submitted for comparison. Writing appropriate case information on the back should identify each sheet. In addition, there should be included any appropriate information concerning the circumstances surrounding the discovery or location of the sheets (masusi ding alamin saan at paano natuklasan ang papel o sulat na nagkaroon ng problema).
Examination by the Laboratory
The chemical and physical process to which paper is subject in its manufacture often provides identifying characteristics, which permit the expert to distinguish one sample from another. By comparing the characteristics of two samples, the analyst can readily determine the dissimilarities and eliminate the possibility of the identity of the source. In some cases, it is possible for him to identify and conclude that two specimens came from the same source.
Some of the methods listed cause a physical change in the document and ordinarily are not used by the document examiner without obtaining specific authorization from the contributor (or court). Furthermore, documents under examination MUST NOT BE TOUCHED with pointed objects that may cause marks like pencil, ballpen, knife or dental picks, and the like, again, unless authorized.
(A) Physical test – the following physical characteristics and measurement serve to differentiate paper: thickness; measurement of length and width; weight per unit area; color; finish such as bond, laid, smooth or glossy; opacity, the capacity of the paper for the transmission of light; (gaano kakapal ang papel, ang kanyang sukat ay hindi pare-parehas ayun sa manufaturer, timbang ng bawat pahina, kulay kung maputi, matingkad ang pagkaputi, maputla o madilim ang pagkaputi, sya ba ay madulas, magaspang, makintab, manipis na kayang tumagos ang liwanag: Tagalog).
Folding endurance as a determined instrumentality by the number of alternate folds will stand before breaking; bursting strength as determined by the measurement of the pressure necessary to burst a hole in a sheet of paper; accelerated aging test performed by means of high temperatures or strong artificial light.
(B) Chemical test – chemical test may be conducted to determine the fiber composition, loading materials, and sizing used in the manufacture of the paper. Like the physical test previously described, chemical tests are of little value unless a side-by-side comparison can be conducted between the paper in question and the known standards submitted for comparison. The use of chemical tests causes a small change or alteration in the document; hence, extensive testing may consume a part of the evidence, and the investigator should indicate to the expert the degree to which the testing may be carried (Tandaan: ang chemical test ay napakadelikado kasi nasisira nito ang papel o bahagi ng papel, kaya hanggat maaari ito ay wag gagawin. Kung sakali mang gagawin ito, siguruhing may pahintulot ang korte na may hawak ng kaso pati na din ang pahintulot ng may ari ng dokumento: Tagalog). The following test is commonly employed:
[1] Sizing test – by the use of a few drops of chemical reagent, the sizing of the two different specimens of paper can be compared. A small perceptible stain results in this test. Sizing is used in papermaking and textile manufacturing to change the absorption and wear characteristics of those materials. (ang sizing ay chemical na inilalagay sa pagawa ng papel para ito ay tumibay at tumingkad ang kulay at iba-iba ang timpla nito ayun sa manufacturer; kung kaya ang papel kapag gawa ng ibang manufacturer at ginamit kasabay ng ibang papel sa dokumento ay maaring makita sa pamamagitan ng chemical test: Tagalog)
[2] Loading materials – the test is performed by burning and ashing the greater part of an ordinary sheet of paper, then analyzing the ash. Obviously, where only a limited sample of evidence is available, this test is not recommended. Inorganic, non-fibrous material added to the paper pulp prior to papermaking. Adding fillers to the paper pulp is called loading. The combination of pulp and filler is called the papermaking furnish. The most commonly used fillers are recycled old paper, clay, and titanium dioxide, the latter of which is ideal for increasing opacity (ang loading materials tulad ng sizing ay magkakaiba din ang timpla ayon sa manufacturer kung kaya ang papel na gawa sa iisa o magkakaibang manufacturer ay normal lang ma madaling makita sa pamamagitan ng pagsunog sa maliit na bahagi nito at pagsusuri sa abo sa pamamagitan ng kemikal o microscope: Tagalog)
[3] Fiber composition – chemical reagents are applied to small sections of the paper in order to determine the nature of constituents of fibers. Fiber composition is wood used in making papers whose major component is cellulose fiber, lignin, and hemicellulose. (maraming klase ng kahoy ang maaring gamitin sa pagawa ng papelat dito sa fiber composition malalaman kung anong kahoy ang ginamit sa pagawa ng papel: Tagalog)
[4] Absorption – strips of the paper are suspended in liquids to determine either the rate of absorption or the total absorption of the paper. (ang uri ng papel ay madali ring malaman kung magkaparehas o magkaiba sa pamamagitan ng paglagay nito sa tubig at alin ang madaling sumipsip o mabasa ng tubig: Tagalog)
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WATERMARKS
The chief characteristic indicating the source of origin is a watermark. It is a distinctive mark or design placed in the paper at the time of its manufacture by passing the paper under a “dandy roll”. Several designs are present on the dandy roll, similar to each other, but bearing individual characteristics, particularly if the roll has been subject to wear and damage.
By examining the watermarks, the examiner is able to identify the paper as the product of a particular manufacturer. (Ang watermark at permanenteng desenyo na makikita sa papel; ito ay espesyal ayun sa kahilingan ng mga ibat-ibang opisina (ng gobyerno o pribado) na lagyan ang kanilang papel bilang pagkakakilanlan ng opisina at ng kanilang opisyal na transaksyon: Tagalog).
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THE INKS, SECRET INKS, AND THE APPROXIMATE AGE OF DOCUMENTS
INKS
In the examination of questioned documents, it is sometimes necessary to investigate questions concerning inks that have been used in the writing. For example, if it is alleged that alterations have been made, it is advisable to compare the type of ink in the disputed original writing with that of the alleged alterations. If the chemical examination shows that two different types of inks were used, the inference to be drawn is obvious (ang ink chromatograph analysis ay isang paraaan para malaman kung magkaparehas ba ang ink o ballpen na ginamit na pangsulat sa dokumento tulad ng larawan sa ibaba: Tagalog).
Another point of interest lies in the questioned age of the inks: is the writing as old as the date it bears; were the writing chronological business entries all made at the same time or over a period of time as would be natural in the course of business? (Sa ngayon ang carbon-dating analysis ay isang mabilis at eksaktong pamamaraan para malaman gaano na katagal ang isang dokumento pati ang ipinangsulat dito lalong-lalo na kung pinaghihinalaan na ang papel at kasulatan o isinulat ay pinagmukhang luma:Isa pa sa maaring problema ay ang mga binura at pinatungan ng bagong tinta sa mga kasulatan tulad ng nasa ibabang larawan, sa pamamagitan ng transmitted light tulad ng infrared makikita kung ibang tinta o panulat ang ginamit: Tagalog)
Finally, it is sometimes of great interest to learn whether a particular bottle of ink was used for the writing on two different documents, e.g., the bottle of ink may be the common source for the ink used on a series of anonymous letters (sa ngayon dahil sa teknolohiya ng pansulat, bibihira na ang gumagamit ng ink bilang panulat maliban sa printer ng computer: Tagalog).
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Another common problem of the police laboratory scientist and the document examiner is the decipherment of the relatively invisible. Thus a stain on a garment or an obscured writing on a document can be rendered visible by the use of a certain technique, this is specifically if the writing is made of invisible ink or secret inks.
Our example here will enlighten the learner on how to detect and develop the secret ink, which is important in the investigation of the questioned document.
The above and below photographs are examples of ultraviolet detection of secret writings or writings due to invisible ink. There are several methods of writing invisibly and can be developed through using pointed rods as a writing instrument and can be developed for visibility through the following:
(a) DEVELOPMENT BY HEAT:
Carefully, heat the pieces of paper without burning them (USING IRON, CANDLE, ELECTRIC BULB HIGH WATTAGE, or STOVE) containing the writings using starch, lemon juice, milk, sugar, cobalt chloride, and sulfuric acid solution.
(b) DEVELOPMENT BY ULTRAVIOLET LIGHT:
Expose the secret inks of silver chloride and note the color produced with the aid of (portable) ULTRAVIOLET LIGHTS.
(c) DEVELOPMENT BY AMMONIA FUMES:
Expose the paper containing phenolphthalein writing, copper chloride, and ferric chloride in AMMONIA FUMES.
(d) DEVELOPMENT BY AMMONIUM SULFIDE:
Expose the writing of cobalt chloride, copper chloride. Lead chloride and ferric chloride on the VAPORS OF AMMONIUM SULFIDE.
(e) DEVELOPMENT BY IODINE FUMES:
Expose the writing of starch solution over IODINE FUMES.
The chemicals are allowed to produce smoke or fumes after heating and let the suspected secret writings suspended just above the bowl. secret writing may slow appear and develop (see the picture below).
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THE TYPES OF INK
The problem of differentiating the inks used in two specimens of writing depends on its solution on an understanding of the physical and chemical characteristics of the major classification of inks. The following types of inks are mostly encountered in document works:
[1] Iron Gallotannate Ink
This type of ink has long been used for entries in record books and for business purposes in general. Iron gallotannate or nutgall inks are true solutions and not merely suspensions of solid coloring matter in liquid form. Hence the ink is capable of penetration in the interstices fibers of the paper thereby inscribing the writing on the body of the paper and not on the surface alone and rendering its removal more difficult. This ink, therefore, is HARD TO BE ERASED.
[2] Logwood inks
From the wood of the logwood tree, a natural coloring material (hemotoxylin) is obtained by extraction with water. The color of logwood inks depends upon the inorganic salt that is added but only after drying and standing they turn black. The addition of chromium salts will yield the deepest black. At the present time, logwood inks are practically obsolete although they are reported to be still in use in Germany.
[3] Nigrosine Ink
This is a water solution of a synthetic black compound prepared from aniline and nitrobenzene. This synthetic type of ink is usually referred to as nigrosine ink and black aniline ink. No new compound is formed by oxidation after this ink is applied to the paper so that lines are merely deposited organic solids that were in solution before the ink dried. It should be expected then that water would affect this ink by redissolving the nigrosine.
[4] Chinese India and Carbon Writing Inks
Inks containing carbon is the oldest writing substance known. Chinese and Indian inks are the most common inks. In modern times finely divided carbons held in colloidal suspension are used to produce deep black drawing and writing ink. Since carbon is chemically inert to the usual testing reagents, it will resist all attempts at oxidation or reduction and will remain uninfluenced by changes in acidity. This type of ink, however, does not penetrate deeply into fibers of the paper, and hence may be washed off.
[5] Ball Point Ink
Because of differences in the construction of the ballpoints pen, different types of inks is required. In place of the fluid type ink, a thick pasty substance is used which will suitable dye to the ballpoint but which will not flow readily. The permanency of this ink is not known with any accuracy, it has been noted that many ballpoint inks have a tendency to fade but hard to be erased.
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COMPARISON OF INKS
To determine whether two documents were written with the same type of ink various physical and chemical methods are available. The inks are compared visually for color.
The naked eye, color filters, and infrared photography usually reveal differences in colors. A 5% solution of hydrochloric acid is the most generally useful reagent. The reagent may be applied with a sharpened wooden toothpick to a small area of writing.
When hydrochloric acid is placed on iron nutgall ink, the color disappears and it turns in light blue. On logwood ink, a red color develops. In nigrosine or carbon ink, there is no reaction. To distinguish nigrosine from carbon ink a 10% solution of sodium hypochlorite is used. Nigrosine ink turns from brown with this reagent but carbon ink is unaffected. It should be noted that this reaction sometimes takes place in a certain period of hours. The investigator should test inks only as a screening procedure where a number of suspected documents are available. This is aside from the analysis of ink through thin layer chromatography (see picture below).
AGE OF INKS
It may be said in general that under ordinary circumstances it is practically impossible to determine the age of inks. A limit can sometimes be placed to the age by the color matching with standards to determine the degree of fading and by chemical reaction, which depends on oxidation. The chemical methods are not applicable to nigrosine and carbon ink, which are not oxidized after being deposited on the paper. In any case, age determination will depend on the composition of the inks, their condition with respect to fluidity and impurities, the nature of the paper used in the writing, and the conditions under which the paper was preserved (as mentioned earlier, carbon-dating analysis is of help in determining the approximate age of the document which includes analysis of paper and inks).
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END OF MODULE 2:
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