Chemistry in Crime Detection J. EDGAR HOOVER
J
Director, Federal Bureau of Investigation United States Depertment of Justice, Washington, D. C
ULIUSCAESARandGeorge Washington, although they lived hundreds of years apart, had much in common in so far as living conditions were con cerned. For both, travel by land was by beast of burden, while by wa.ter, animals or the wind furnished the power. Soures, of light were similar for each. The his tory of man stretches backward for thou sands of years, yet only relatively recently has the human race enjoyed the benefits of living provided by science. In this scientific awakening chemistry has made many contributions to the development of scientific crime detection. Law enforcement within remit years has become more effective because it, too, has shared the gifts of chemistry. The chemistry employed in this field cannot be considered a sc|>arate and distinct branch of this versatile science, for indeed all of its branches make their contribution to the just enforcement of the law. Ver satility itself is a requisite of the crime de tection laboratory, if it l· to enjoy the full benefits which chemistry and the other sciences have to offer. The Technical laboratory of the Fed eral Bureau of Investigation v.as estab lished in the fall of IU32 to assist in the criminal investigations conducted by the special agents of the I· HI. The facilities of the laboratory early proved of material assistance in many types of cast·*, and in creasing demand for scientific aids war ranted rapid increases in both equipment and personnel of the laboratory. The scope of scientific work ικτformed soon was enlarged and, iu addition, the facili ties of the lal>oratory were extended to all police and law enforcement agencies in the United States and its |>ossessions. In view of the great variety of scientific problems received in the Technical labo ratory, it was necessary to select as mem bers of the technical staff individuals who, by reason of experience and training, rep resented the viewpoints of various fields of science. Consequently, many branches of chemistry arc found and versatility is assured. Laboratory procedures are usually or thodox methods borrowed from some branch of chemistry and, through special application, adapted to law enforcement. For example, a well-known test for nitrites uses reagents of sir fan die acid and anaphthylaminc which produce a red coloration by the formation of the diasonium salt in the presence of a m tri te. The blast of gases from a gun muzzle held close to a person will deposit nitrites on the clothing and form a pattern, iierhaps invisible, which will be of assistance in estimating the firing distance of the gun.
Gelatin-coated paper is treated with solu tions of sulfanilic acid and a-naphthylamine and placed in contact with the area of clothing surrounding the bullet hole. The clotb is permeated with acetic acid vapor and a pattern of red spots will be formed on the paper corres|x>nding to the nitrite deposits on the cloth. The closer the gun was to the individual, the smaller will be the pattern of red spors, and vice versa. A similar and perliaps more direct chemical procedure is the application of photographic chemistry to the develop ment of latent fingerprints on porous or absorbent surfaces obviously not respon sive to mechanical methods. This photo chemical reaction is based on the fact that sodium chloride is a constituent of the se cretion deposited by the finger ridges. A silver nitrate solution applied to the se cretion will, of course, precipitate silver chloride and upon exposure* to light the free silver will outline the design of the finger ridges. Frequently, this procedure is preceded by fuming the finger impres sions with iodine vapor, which causes some of the organic constituents to become visible. One of the greatest obstacles to the aj>-
plication of chemistry in crime detection is the limited quantity of samples. Too frequently a sample of only a few milli grams is available where a complete quantitative analysis is desired. For this reason, the usual chemical methods are often supplemented by other types of ex aminations, such as the microchemical, spectroscopic, microscopic, cryetallographic, and pétrographie. The problem of the laboratory technician varies, how» ever, depending upon whether identification or elimination is the primary consideration of the examination. In the former, where it is necessary to show two substances to be alike, complete qualitative and quantitative examinations are indispensable. It is usually possible, however, to show that substances are dissimilar by a specific test sufficient to reveal only one qualitative or quantitative difference. Iu surveying the importance of chemistry' in law enforcement work, one should give consideration to the contribution· of analytical methods—inorganic and organic. We may find chemistry identifying substances left at the scene of a crime, which substances, when traced to their sources, may indicate the occupation or location of the criminal. These instances, of course, may range from examinations of soil, which may suggest a particular area, to determinations of greasy substances on a mechanic's glove. Comparisons are also made to link suspects with a particular crime. Special apparatus is maintained in the Technical Laboratory to remove dirt and debris from clothing in order that, among other things, putty or plaster may be chemically compared with materials at the scene of the crime which may have been disturbed by the criminal in gaining entrance to a building. Examinations of paint samples are frequent in efforts to show that a quantity in possession of suspects is similar to or different from that used to change number· on automobile tags or to mark the I>ay-off spot in an extortion case. Metal shavings removed from the erankcase of an airplane motor can be compared with waste in a
Upper. Chemists analyze evidence at the Technical Laboratory of Federal Bureau of Investigation. Lower. Technicians examining crime evidence in the Chemical Laboratory Section of Technical Laboratory· 402
May 10, 1940
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Left. A laboratory technician analyzing stains found on an en velope. Below. Washing bloodstain through fabnc onto paper for subsequent preliminary testing with benzidine-hydrogen peroxide. Both photographs shown at the Technical Laboratory of the Federal Bureau of Investigation, United States Department of Justice.
machine shop. Inflammable liquid* in anon cases and explosive materials in at tempted bombings are subjected to labora tory examinations to provide information for the investigators of the particular crimes. Organic chemistry and biochemistry have made valuable contributions. Blood chemistry is a prominent phase of labora tory work. Progressively we may see pre liminary and confirmatory tests for blood, procedures to show the human or other origin of the specimen, and the grouping of human blood. An alcoholic solution of benzidine, leucomalachite green, or phenolphthalin (reduced form), together with hydrogen peroxide, gives intense colors in the presence of a minute quantity of blood. Crystallizing the bloodstain from glacial acetic acid, containing chloride, gives characteristic crystals confirming the presence of blood. Procedure to establish the origin of blood employs antisera which are prepared in the laboratory by injecting over a pe riod of weeks a blood of known origin into laboratory animals, after which the serum of the animals' blood is used in the pre cipitin test. This test may be conducted by adding to a small test tube containing a solution of the stain a small amount of the antiserum. An opaque ring at the junc tion of the two liquid» will indicate that the stain is from the same animal species as the blood injected into the animal. In practice careful control is necessary in evaluating the sera, and a number of con centrations of the stain are used to deter mine the maximum dilution giving the precipitin test. Special techniques are necessary in grouping, inasmuch as the unknown blood is frequently dried or absorbed in clothing.
Similar procedures are applied to other body secretions known as group specific substances which include, for example, saliva on the end of a discarded cigare t. Toxicology is a chemical study devoted largely to law enforcement. Here, again, procedures permit the separation and iden tification of volatile, inorganic, and or ganic toxic substances by methods which parallel other analytical schemes. Scientific proof of intoxication has long been desired. Though laboratory results require medical interpretation because of variance in physiological effect, accurate determination of the amount of alcohol in blood, urine, or spinal fluid is accom plished. One method employs the famil iar reaction of oxidation by an excess of standardized dichromate solution and ti tration of the remaining unreduced di chromate. Determination of carbon mon oxide in blood is useful in determining the cause of death. Physical chemistry plays its part in crime detection, the determination of solu bilities, melting points, and other physical properties being of much assistance in analytical methods. Electrochemistry may be used as an example. Frequently burglar tools used in gaining entrance to buildings or repositories leave detailed impressions characteristic of the particular tool. This impression, or a reversal to simulate the tool, may be made witl plastic materials which are then coated with a conducting medium and placed in an electrolytic bath. A metal duplicate of the impression or replica of part of the tool is thus made available to the investi gator. Hydrogen-ion concentrations may be an additive factor in the comparison of substances, or may indicate the decompo sition of blood or other putrefying matter.
Chemistry has other applications to law enforcement besides laboratory examina tions of physical evidence. As a result of laboratory tests it was found that several dyes and chemical indicators were adapt able to a procedure used by investigators in tracing stolen merchandise. For ex ample, a solution of an indicator can be added to a storage tank of gasoline in quantities which are not visually detect able or do not interfere with the proper function of the fuel. Samples taken from the automobile tanks of persons suspected of having stolen gasoline from the supply tank may be tested by shaking with an alkali which will separate as a colored aqueous layer if the gasoline is from the supply tank. Similarly, dyes in dry form may be dusted on objects which the crimi nal may handle in the course of a crime, and may afford a rapid solution of the case if the criminal is later observed to have staged hands. As in all chemistry, research is a guiding light, simplifying present procedures, providing improved methods, and point ing fie way to additional application o.' this science to law enforcement. Though the Technical Laboratory of the Federal Bureau of Investigation is constantly en gaged in efforts to broaden the scope of its work, new methods do not necessarily originate in the laboratory dedicated to law enforcement. A new application may be accredited to a chemist far removed from law enforcement work and engaged in some brancL of industrial chemistry. Hence, the value of chemistry, of science as a whole, is ever increasing in crime de tection and on the basis of past develop ments we are hopeful cf the future.
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Hazards with Butadiene and Its Peroxides D. A . Scott, Shell Development Co., Emeryville, Calif. CERTAIN information concerning unusual hazards which may be encountered in working with butadiene and related compounds has come to our attention and is recorded here for the benefit of others. Butadiene, when heated under pressure may undergo violent thermal decomposi tion . 1 η one instance, explosive decompo sition with carbon formation occurred on heating butadiene in a stainless steel bomb, while previous similar exj>erimente gave no unexpected occurrences. Per haps enough material was placed in the bomb so that it became entirely filled with liquid on heating, and the hy drostatic pressure may have initiated a decomposition similar to that taking place in acetylene upon compression. No ex plosions resulting from heating at atmos pheric pressure have been observed in the absence of oxygen. , In contact with air or oxygen, butadiene may form violently explosive peroxides and may be detonated by either mild heating or mechanical shock. Solid buta diene, exposed for a very short time to
oxygen s>t subatmoephehc pressure, ab sorbed sufficient oxygen so that on warm ing slightly above the melting point a violent detonation occurred. It is sus pected that this behavior of butadiene is influenced strongly by the accidental pres ence of oxidation catalysts or inhibitors. Addition of an inhibitor to butadiene which is to be distilled or allowed to stand in con tact with air or oxygen, even at low tem peratures, would help avoid explosions. After emptying a storage tank of crude butadiene, some polymer was found at the bottom. The polymer contained 0.095 equivalent of peroxide oxygen per 100 grams and could be detonated easily by a hammer blow. The polymer containing the oxygen compounds was insoluble in the butadiene, and the butadiene itself showed only a trace of peroxides. The peroxides probably were formed by re action between butadiene and air. Sub sequent investigation showed the peroxide could be destroyed safely by treatment with strong caustic soda (48° Be.; 47 per cent sodium hydroxide).
Standard for Fuel Oils
Fire-Retardant Paint
RAPID progress made by American oil refiners and scientific laboratory to ward uniformity in the quality of fuel oils has necessitated a further revision, of the commercial standard for these products, the National Bureau of Standards has an nounced. The standard for fut 1 oils was originally published in 1929, but as oils, used for heat treatment, glass and ceramic furnaces, and other special purposes sometimes involve a low sulfur requirement, the standard was revised to carry a table showing permissible maximum sulfur content for each grade as a guide to the purchasers. This revi sion was published in 1933. There were later revisions, and now another one is under wav.
OF
A PROPOSED simplified practice recommendation on color marking for anesthetic gas cylinder has been submitted to producers, distributors, users, and others interested, by the Division of Simplified Practice of the National Bureau of Stand ards for consideration and approval. This recommendation was submitted by the American Society of Anesthetists, with the approval of the Committee on Simpli fication and Standardisation of Hospital Furnishings, Supplies, and Equipment of the American Hospital Association. Iden tification by color or a combination of colon, is provided for seven different ι itjid two mixtures of gases.
Objective Tests in Organic Chemistry T H E 1940-41 series of the Cooperative Objective Tests in Organic Chemistry is in preparation. It is believed the pres ent series will meet the need of the aver* age instructor of organic chemistry some what better than the teste of this series previously prepared. It is hoped» fur thermore, that those who use these teste during the coming school year will cooper ate to the extent that this series may be standardised and the validity of each item determined. One page is devoted to each of 26 topic examinations in organic chemistry, and 3 pages each to the final examinations for the first and second semesters, malting * total of 32 mimeographed pages to a set. These sets are available to instructors and graduate students or research workers in lots of 5 or more at 20 cents each, f. o. b., Lafayette, Ind. Single sets are 3o cents. Those using these tests in their classes will be provided with a key for convenience in grading. If you are interested in examining or using the 1940*41 series of Cooperative Objective Tests in Organic Chemistry, place your order with Ed. F. Degering, chairman, Cooperative Objective Tests in Organic Chemistry, Purdue University, Lafayette, Ind.
MANY formulations for fire-retardant
paint prepared and tested at the United States Forest Products Labora tory, Madison, Wis., the most satisfactory are linseed oil paints containing finely ground borax. Although these paints will not protect wood effectively against continuous exposure to high temperatures, they do afford considerable resistance to the spread of small fires. Paints containing white lead as pig ment have given best results, but those uring titanium or zinc sulfide pigments also are effective. Typical formulas of fire-retardant paints are:
Pigment
Color Marking for Gas Cylinders
Vol. 18, No. 9
Borax RAW linseed oil Turpentine Japan drier
*
(Basic carbonatewhite lead) 41.0 32.0 22.8 3.6 0.6
To secure maximum fire protection, at least 8 gallons per 1000 square feet (3 or 4 thick coats) are required. At this rate 1 gallon will cover about 125 square feet. These paints are not satisfactory for ex terior use because rain leaches out the water-soluble borax and the degree of fire retardance decreases with exposure. Al though white lead-borax paint retains its fire-retardant effectiveness after 30 months' exposure to different interior humidity conditions, much additional information is needed to perfect it. The
H - O - H Lighthouse THE H-O-HLighthouse,bimonthly house organ of D. W. Haering & Co., Inc., Chicago, Ill., is being introduced this year in a new format and on a new quarterly publication schedule. It is devoted to the dissemination of accurate information on recent developments in the scale, cor rosion, and proportioning fields. The new quarterly has been modified in sise to fit the pocket, increased in pages to en large the scope, and illustrated with pic tures and sketches to increase interest.
— % by Weight (Titaniumcalcium) 3 0 . 0 35.0 30 8 3.6 0.6
·
1
•
»
(Lithopone)24.0 39.5 32.3 3.6 0.6
paint yellows indoors but this tendency can probably be reduced by modifying the vehicle. Inclusion of a chemically active ingredi ent as borax is unoi .hodox from a manu facturing standpoint, but painting proper ties and fire retardance of paints stored in a can for 1 year equaled those of the freshly prepared product. This type of paint is still in the developmental stage. Its use is recommended only where resist ance to fire is of greater importance than other properties.
