Forensic chemistry: An introduction to the profession

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Forensic Chemistry-A symposium collection ---

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Introduction to the Forensic Chemistry Collection Thr articles i n this rollrrtwn emerged 25 a r e d t of 1noS)mpo.i~ un f~~rrns~cchemisrry-the fir%twas held asa par1 of the 78th AI'S meeting in Sruttir, U'dahingtun, i t , hlarrh. 1Yd:l. mu t h e s e n d at the oth BwnnralCanf~rence irn rhpmiral cdurarim in Srcrrrs, Connrctirut, in uyust. ID3 I. 'l'hr objectivv uf thi* toilwtim i\ tu prwrdc teacher* otchemistry with ample resource material so that they might add forensic chemistry units to enhance the relevancy of their courses and introduce forensic chemistry as a profession and possible career choice for their students. Topics range from development of forensic science laboratory courses and mock-crime scenes to forensic serology and analytical techniques.

Keith Berry

Henry E. Outlaw

Department of Chemistry University of Puget Sound 1500 N. Warner Tacoma, WA 98416

Depanment of Physical Sciences Delta State University Cleveland. MS 38733

Forensic Chemistry: An Introduction to the Profession Keith Berry University of Puget Sound Tacoma. WA 98416 George G. Ishli Western Washington Crime Laboratory seanle, WA 98104 In this oaoer we hooe to communicate some of the characteristics df the profession of forensic chemistry, and some of the requirements f w persons in the field, from the viewooint of an kducator, a practitioner, and a laboratory director. This information may help persons interested in the discipline or the profession make judgments for further action. While forensic chemistry is essentially the application of chemistry to all matters of law, we will limit ourselves to the area of criminal justice, thereby foregoing any discussion of civil procedures and requirements. The California Association of Criminalists describes the profession as "That orofession and scientific discioline directed to the resoynilion, identification, individualization of the and evnluarion ofnhvsiral e\,idence hv the aoulicntion .. natural sciences to caw-science I t further states, "It involves the application of principles, techniques and methods of the natural sciences, and has as its primary objective a determination of physical facts which may be significant in legal case^."^ Characterlsllcs of the Profession Forensic chemistry and analytical chemistry consider similar auestions includine" what andlor how much of a given item is in a given sample. There are, however, several other important anestions with which forensic chemists are concerned. ~ h e would k like to know what the sample originally was, where i t came from, what was the source, and how it got from one place to another. For instance, a chemist may he able to determine if a particular liquid is water; the forensic chrmisr may wish to know where &at water came from. To do this he or shr will have to harea method to determine, for

example, if i t was lake water, sea water, water from a particular chemical synthesis, or from a particular chemical processing plant. The forensic chemist is likely to he interested in whether the sample shares a commonality of origin with another sample on hand. He or she is likely to he interested in finding a reasonable explanation for its presence a t a oarticular place and will be-interested in experiments that wiil connect or relate the sample or evidence to the victim or suspect. As society has-aged and technology has advanced, there are solutions now available for problems that used to he unsolvable. Problems related to the examination of nhvsical evidence from crime scenes persist in providing interesting challenaes for chemists. We will illustrate a tvoical case. Consider a case in which a driver in a sto~eiEarstruck and killed a pedestrian. The impact was so areat that the driver struck his head against the windshield breaking the glass and cutting his head. He fled the scene and there were no witnesses, but due to the severity of the injury he went to a hospital for treatment. During the police investigation they questioned a doctor and nurse who had treated a patient with a head injury; the nurse had shaved hair from the suspect's head and had not yet disposed of the hair. Examination revealed that the hair had not only been cut by the nurse a t the hospital, but at the other end of the hair shaft glass fragments were adhering to the hair. The glass was compared with samples taken from the windshield, while the hair was compared with hair samples removed from the car. Both types of samples compared favorably, the hair being consistent with having come from the same origin, the glass fragments exhibiting the same physical properties (density, refractive index, optical dispersion) as that from the windshield. Essentially, the chemist answered such questions as what the material was, how it got there, whether it was there at the time of impact, and whether there was a commonality of source. Forensic chemistry requires knowledge of other disciplines. Biochemistry is used in bloodstain

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' Kingston, C. R., A.S.T.M. Standard. News, 1 [4], 8 (1973).

Davis, J. E. (Editor),"Code of Ethics," California Association of Criminalists. adopted May, 1957. Volume 62

Number 12 December 1985

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analysis and examination of other body fluids. Biology is required for examinations of human tissue, physiological fluids, vollen. and leaves. Phvsics is used in crime scene recon&ction, velocity analysis, and meterology and for determinina the amount and direction of force. Materials science is iequired during the examination of concrete, paint, glass, dyes, and ceramics. Anthropology relates to the examination of teeth, hite marks, and hair. Statistics and probability are important when considering the frequency of occurrence of artifacts and distribution patterns. Geology and microscopy are other important disciplines. Special Problems and Consideralions Attributes that make forensic chemistry challenging, and a t times frustrating, are illustrated by some of the special orohlems faced in the laboratorv. Consider the orohlem of sample diversity. This is as important as any other in making forensic chemistry fascinating to the lay person and the practitioner, hut a t the same time it produces many problems. Anvthina in the environment is ootentiallv a forensic sample and may he the subject of an examination. Samples, often with no history, are brought into the laboratory possibly after having been handled by one or more persons. The samples may be altered inadvertently or knowingly. Samples may he contaminated. The environment may interfere with the sample during the processing of physical evidence. Only rarely does one have any control over the size of the sample. For example, a gun powder residue on a victim's clothing contains a limited amount of material. One would want to do chemical testing for cellulose nitrate and sodium and potassium nitrate or nitrite. Chemical tests for those components are relatively straightforward. One may want to examine the pattern of disbursement of particles around the wound hole. This is a typical physical examination. Then one might need to form an opinion about the distance from which the gun was fired. All of these must be done with a small amount of sample. This example illustrates the multidisciplinary approach required by small samples. If one examines several fragments of metal, can one draw conclusions regarding some missing fragments? There is a very strong temptation to do so, especially when all the fraements in hand exhibit uniform nronerties. T o extraoolate and conclude that all missing pirtiiles are identical has caused manv nrohlems and is an undesirable oractice. Quite often one has-no information other than thadthe parti&lar material was found at the crime scene, and the question is, ..Is it rrlevant to thesperifiratiun ofeventsthat took placr at somr time in thr past?" 'l'his is pnhnhly the most rhallenring area for the forensic chemist. There are some important questions in which the chemist must always be aware. One is the nature of the examination. A result must be evaluated and interpreted in light of all information available to the investieator and the forensic chemist. This evaluation and interp;etation is the heart of the whole nrocess and reauires the chemist to he imaeina" tive, creative, and willing to pursue the problem to its conclusion. Situations arise where analytical results are very similar, hut conclusions vary. For instance, paint samples may exhibit nearly the same infrared spectrum but have a different color. Those who rely only upon similarities, as demonstrated by the instrumental data, may have difficulties of this kind. There may he subtle differences, too. Sometimes those small differences may appear not to he significant. The question is, "Are they relevant to the situation?" One must he careful to explain apparent unusual characteristics. Uniqueness literally means "one of a kind." I t is easy to say that something is unique, hut extremely difficult to prove. If one does not have resources to justify such a claim, the claim should not he made. Thus, one may need to approach the problem of demonstrating uniqueness from a different perspective. 1044

Journal of Chemical Education

After one does all of one's work. one must renort the results. One must work within the ruies of law to aslure that the results are accentable to the court. For instance. if one testifies that marijuana was present in a sample, it isn't sufficient to say, "The green material is 'grass' or 'pot'." Such a statement doesn't meet legal requirements. While some states are more rigid than others in this regard, one must mention either the chemical constituents or perhaps the official name of the plant that was examined. There may he another problem with the wording of a given response or of a written report. Sometimes the scientific point is correct, hut from the legal perspective i t may not only he improper and inadmissible but also devastating to the person for whom the report was written because it is vulnerable to legal attack. Ouallflcatlons for the Profession Having discussed typical problems and characteristics of the profession and having given some examples of the types of examination that are undertaken by chemists, we now turn our attention to the qualificationsneeded for a typical position. Of course, the candidate must have a solid and high quality scientific background and an education that exhibits the multidisciolinarv aooroach noted earlier. There must he .. substantial strength in chemistry; we suggest an ACS-certified decree a t the undereraduate level. The candidate must iave the ability to think creatively. Too often we rely on instruments, without evaluating their limitations. The human computer, the brain, remains one's most valuable tool. Employers seek persons who continually search for new and different methods, different applications, or different perspectives. They want people who seek opportunities to apply known techniques in novel ways, for instance. The candidate must exhibit good judgment. We stress the very serious concern that one avoid pushbutton technology for the sake of heine "modern." There is a temotation to produce massive amounts of data, the assumptionbeing that the more data one produces, the better the result. We assert that it is the quality of the data that defines the quality of the result. I t is the quality of the data that vroduces confidence in the answer br co&sion. Finally, we wish to suggest that the forensic chemist must he able to work independently. The chemist frequently works with others, often on the same case, and i t is true that beeinning chemists often work with a senior laboratorv oerson. ~evertheless,the person who is sufficiently mature, motivated. insiehtful. and efficient to work hv her or himself has a talent that will be recognized.

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The Literature of Forensic Science Kelth 0. Berry University of Puget Sound Tacoma. WA 98416

When I brgan tearhing forensic science several years ago, 1 found that one of the most difficult problems I faced was to find and acquire suitable and modern references, both for mv own use and as references that I could cite for student examination. Since any teacher interested in presenting a course for students will face that same problem, this paper contains sueeestions to helo them eet started. Local. municipal, state, or federal crim'e lahotkories can provide some information. My experience has been that criminalists and

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