edited by FRANK S. QUIR~NG Clayton Hgh School Ciaytan. MbsrOur8 63105
a place for cherni~t~ Forensic Chemistry R. C. Briner SEMO Regional Crime Laboratory, Southeast Missouri State University, Cape Girardeau, MO 63701 An Exciting Profession Forensic chemistry is a subdivision of the larger field called forensic science. This field applies the principles of natural science to matters of legal debate. Forensic science has also been called criminalistics, and forensic scientists called criminalists. Because of the similarity in names, the field of criminology is often confused with criminalistics. They are not the same. Criminology is a social science which involves why people do the things they do. The work of the forensic laboratory can he broken down into the following areas ( I ) : identification of materials or substances encountered as evidence comparison of substaneesor materials to try to establish a common origin individualization of articles of evidence reconstruction of aset of past events through analysis of physical evidence. Implicit in each of these tasks is the understanding that each crime laboratory be able to provide the criminal justice system w i t h the best possihle analysis of the evidence, so that the "triers of fact" (jury) have the best possible information from which to make their decisions. A Historical View
Forensic science has heen around for many years. The "police lab," as i t was often called, was usually a small photo lab in which the "police chemist" would work in the areas of fingerprints and photography. Eventually this field expanded to include examinations of firearms and microscopic comparisons of expended slugs. The influx of drugs into society during the late 60's and early 70's had its impact on forensic science which resulted in an increase in the numhers of chemists and chemical technicians needed to carry out the record numbers of drug analysis. In many crime laboratories, drug analysis often occupied 75-95% of the work load. As a result, many new laboratories were established in order to meet this increasing demand. In order to understand the operation of the drug analysis section of a crime laboratory, it is necessary to be familiar with the Uniform Controlled Substance Act under which most states operate. Drugs or "controlled substances," as they are now called, are divided into five schedules (see Table 1).In order to place a substance into the correct schedule, the forensic chemist must not only identify the class of the drug, hut also specific structural information about the drug. Recently, a large influx of structural "look-a-likes" has appeared on the market and has made this identification more important. These preparations are made to look like amphetamine, methamphetamine, or another controlled material but contain only ephedrine, phenylpropanolamine, and caffeine (none of which are controlled) (see Tahle 2). Instrumental methods commonly used in the area of drug analysis include ultraviolet and infrared spectrophotometry,
Table 1. Schedules of Controlled Subslances Schedule
Examples
i
Heroin. LSD. Mariiuana Ampnelam ne. Pnenc)cIo ne, Me1naq.a one, and Secooarola BmLpnFtBmine, G Jlctn,m~Oe Va um (d.azepam.-8orium (Chloroiazepoxidcj Codeine Cough Syrup
iV V
CMltrolied substawes are ~suallycias~ifiedinto the above f i e ochedules accord#%to the Un8form Contmlied Substance Law.
Table 2. Structural "Look-a-Likes" Uncontrolled substances
Controlled substances
CH.
I
Phenylpropanoiamine
NH, Amphetamine
Ephedrine
Methamphetamine
AHCH,
nuclear magnetic resonance spectrometry, and mass spectrometry. The impact of gas chromatograph/mass spectrometry in the field of forensic chemistry has been most dramatic in the area of drug analysis. The use of this instrumenintion interfaced with a computer it1 ~ I I Iinteractive mude ha* dmmntically changed the look and uutptn of the furenair drug laboratory. Although the forensic chemist is basically an analyst, he differs from other analysts inasmuch as he is required not only t o identify substances but also to match them with similar items from elsewhere. Moreover, he has to choose methods
.
About the Aulhor.. Robert C. Briner is the Director of the Sourneast Missovi Regional Crime Laboratory located an Uw campus d Sourneast Missouri State Univmity in Cape Girardeau,Missouri. He received a BS in chemisby. Indiana University, Bioomington, Indlana. 1961, and a PhD in organic chemistry, Florida State University, Tallahassee. Florida, 1966. He is currently president of the Missouri Association of Crime Lab Directors (MACLD), past vice-president of the Midwest Association of Forensic Sciences (MAFS),and past vice-presidentof the American Society of Crime Lab Directors (ASCLD). Dr. Briner has been a member of Uw American Chemical Saciely falhe pst 20 years and an the Technical Advisory Committee for Law Enforcement, international Association of Chiefsof Police (IACPI. He has been involved in law enforcement since 1971 and is also on the graduate faculty at Southeast Missouri State University and Southern iiiinols University, Carbondale. - -
Volume 59 Number 1
January 1982
41
which are highly discriminating so that the chance of accidental matchineu is minimized. The modem crime laboratory provides the means to analyze very small amounts of material. The major limitation in the initial search of any item is unually the ability to find the traces of substances which subsequently will be examined. Development in the use of more discriminating tests, the estahlishment of data or information banks on thematerials under examination, and the development of quality controls of laboratory methods have greatly increased the reliahility of this procedure (4).
uf antipwimtihody reac,tiuni :> quite usetul iur ARO typing . Imrr and in wries identiticati~mli.e.. 111~11or a n i m d ~This determkation is quite important in forensic science because the nature of a blood stain is often unknown but a key. . point in an investigation. I t is interestina that the importance of blood stain analysis h.ts heen discusswl in recent urtivli~.in popular rn:~:.rzilies 13, /;I, These h a v ~ trndvd I,, coorev I,. the 1:1\ rt.:tder the imliortance of these new techniques A d their potential impact on the criminal justice system as well as the excitement of working in this field
Crimes against Persons and Propertles
Trace Evidence Another area of forensic science that involves chemical analvsis is trace evidence. Trace evidence is transfer evidence suchas paint, hair, fiber, glass, soil, etc., which can be left by the suspect a t the crime scene or taken by the suspect from the scene. This type of evidence is often useful to reconstruct a series of events (i.e., to place a person at the scene of acrime). The analysis o1'tr.lzeer.idencei\i a omprntii c trchniqtx. ..rncp it is w e d in stttlnrnina r o ,how th:n tat) pieces UI c\.idenre had a common origin.^ piece of trace evidence generally has two components: organic and inorganic. The organic component is usually a polymeric material which can be "finger-printed" by pyrolysis gas chromatography. This technique thermally breaks down the polymer into identifiable fragments which are then separated by gas chromatography. The fragmentation is carried out a t 800-90O0C in the injection port of the gas chromatograph. The volatile fragments are then separated by the chromatograph to produce a "pyrogram" or "fingerprint." Paint, fibers, plastic, and rubber are commonly analvzed bv this techniaue (7). Analysis of the inorganic component of trace evidence involves the identification or "fingerprinting" of the elemental composition. X-ray fluorescence is often the technique used to produce this "elemental profile," because it is rapid, requires little or no sample preparation, and is non-destructive. This technique is useful at elemental concentrations of 100
.
"
in tht. ;u~alysi,of widenre. ty,., drug=,hair, p ~ t i n~1.b~. ~, filn~s, ~lnmnnblrmitierial,, explo:tves, m d biol~egicdrluid. hhrlrrn im.rlytiral methods have exrmdcd thv idea,,! fingerprilitin: i r m peimle to r~hsiicalmstcri;lli. In [hi\ .hilt. tnnttv hlluratories are now biginning to give more emphasis tomimes against persons and properties (referred to as Part 1crimes), and are applying their drug-related instrumentation to other areas of criminalistics including- forensic serology, .. trace evidence, and toxicology. Forensic serology includes all examinations of hlood and body fluids (semen, saliva, urine, and tears). Identification and attempts to individualize samples are done by classical and modern biological and biochemical methods. Electrophoresis is one of the most important procedures used in forensic serology. It allows for separation of charged species, i.e. proteins, through application of an electric field. The greatest use of electrophoresis in the crime laboratory is for separation of enzymes. Many enzymes such as: phosphoglucomutase (PGM). adenvlate kinase ( A H . ervthrocvte acid . nhos~hatase . (EAP),' and adenosine deaminaie (ADA) occur as genetic variations. (These enzymes are known as isoenzymes.) Electrophoresis permits the separation and eventual identification of these genetic markers. The adaptation of these techniques (i.e., biochemical genetics) to dried blood stains has allowed for the identification of the aenetic variation in many dried hlood samples and can often Fesult in discrimination bktween bloods of the same ABO type which might be found at the crime scene (Fig. 1). Immunological techniques are also employed in the identification and typing of biological materials. The specificity
..
.
.,
Figure 1. lsoenzyme typing of blood stains. The abiiity to detect genetic markers in blood stains in addition to ABO types has proven to be a valuable aMiion to b e mime laboratory. It has proven to be useful in elimineting suspects and delineating between two suspects or suspect and victim. The enzyme erythrocyte acid phosphatase (red cell) catalyzes the hydrolysis of phosphate esters in the bcUy and occurs in 6 genetic variations, 5 of which are shown above.
42
Journal of Chemical Education
samole Fioure 2. Tvoical arson analvsis. A one cubic centimeter bm31 .~ .~ .~ of me bapor ,pea0 space aoovc !ne ren8a.e from a wspec'eo arson s n.ec:cd mo a gas cnromatograpn eql'ppca w 01 a f 9PPP on ulllon oe'ector an3 .a 6-11co .mn I ec wlh 3' carbopacr 60 80 mesn proodces 3 panern i f ngerorint n o cn can be identified aslotype of volatile accelerant used. The temperature ofthe Column is programmed between 100-25O0C at lO'lmin heating rate.
ppm (parts per million) or greater, and can identify elements from fluorine (Z = 9) to fermium (Z = 100) in a very short period of time (usually 10 minor less). The technique of X-ray analysis is accomplished by irradiation of the sample with an electron beam (tube or electron microscope) of 2 0 4 0 KeV (thousand electron volts). The X-rays emitted from this irradiated sample are characteristic of the elements present. These X-rays are characterized either by energy difference or wavelength difference. Other methods possible for "elemental profile" determination include emission spectroscopy, atomic absorption spectroscopy or flame emission spectroscopy, all of which are destructive to the sample. Chemical analvsis is useful in suswected arson cases.. Dar. ticularly to provcde evidence of a volatile accelerant used to start a fire. The detection of an accelerant in the debris from an arson fire can be accomplished by a gas chromatographic analysis on the "head space" (the vapor above a sealed sample of residue from the fire) (2). This "head space" analysis often avoids the use of concentration techniques such as distillation (Fig. 2). The identification of gunshot residue or elements present on the hands of persons having fired a hand gun have been areas of great interest in the crime laboratory for a long time. This area of analytical chemistry involves the detection of the elements of antimony, copper, lead, and barium. Instrumentation such as neutron activation analysis, flameless atomic absorption, and scanning electron microscopyIX-ray fluorescence have been used to detect and auantifv these elem e t u s . Huwe\vr, n cent wurk h;t, -how11r h ~ t t It~.frtrchemical anal\.-i~,a l x c i i i t x l l ~m t d ; ~ t r .t t ~ r l"i l\t~rt h , t m i n t1 r v l.\.i\').
Figure 4. lmmunoassay. immunoassay techniques use the selective affinity of the antibodies for specific molecules to achieve accurate measurement of trace amounts of chemicals in bioloaical samoies. The druq (antigen)is labeled with some tag (i.e., radioactivity, enzyme. etc.)
rdn
detect the presenEe of antimony, copper, andiead oh the hands of individuals (Fin. 3). This method allows rawid . wreliminary examination a i d screening of suspects. The qualitative information can later be supplemented by further quantitative analysis (3). This technique can be used to detect many elements and appears to have great potential for the forensic science laboratory. The analysis of trace evidence is quite a diversified application of analytical chemistry which allows the forensic chemist to he limited only by his own ingenuity and imagination. It represents one of the most challenging fields of applied analytical chemistry known. A
Figure 3. Anodic stripping voltammetry (ASV). The use of anodic stripping voltammetry (ASV) to detect nanogram quantitlesof lead, copper and antimony from the hands of individualswho have handledor fireda weaoon. ASV involves atw-step process. ( 1 ) wxcnccnraton Plat nglol me eernenls ootoa nrrc.r) +:cclrode sdfacefollorvea o/ 21 ilrtpp ng of thee emenl from the t: c 3 ! 0 3 c surface. me voltage at which the element is removed is dependent on the electrolyte (4NHydrochloric Acid) and the element itself. The above trace shows all three elements (Pb: -0.59; Cu:-0.31; Sb: -0.21) relative to reference electrode AgiAgCl. ~
~
Figure 5. Gas chromatographylmassspectrometer. The elecb-on hagmemation oattern or "finoerorint" is determinedvia a the oas chromatoaraohic seoaration
An example from a drug sample is shown below. Sample was provided by Forensic Science Foundation. Rockville, Maryland. Analysis counesy ot Randall Robbins, Bureau of Scientific Services, illinois'Wepmrnent of Law Enforcement, Fairview Heights, Illinois, 62208.
Volume 59
Number 1 January 1982
43
competitive binding between the radio-labeled drug antigen with the antibody which is specific for that drug. After precipitation, the mixture is counted with a gamma counter or scintilation counter. Quantification is possible by comparison with a set of standards. In E M I F assay the toxin is labeled with an enzyme. When this toxin-labeled enzyme becomes bound to the toxin antibody, the enzyme is inactivated. The free toxin in the sample competes with the toxin-labeled enzyme for this antibody. An assay of the free unbound enzyme is then determined through reaction with a known substrate. This determination gives specific information about the amount and kind of toxin present. Specific identification of unknown toxins in a blood, urine, or tissue sample is usually accomplished by use of a computer-assisted gas chromatographlmass spectrometer (Fig. 5). Data obtained from such analysis is compared with that in standard data libraries. The Challenge Figure 6. Student Assistant looking at fiber and hair samples under polarized microscooe.
Forensic Toxicology The analysis of drugs or poisons in biological fluids is the prime responsibility of the forensic toxicologist. The problem involved in this area of analysis is the detection of a chemical "needle" in the biological "hay stack." The ability to detect and identify the foreign material in a biological matrix with both aualitative and auantitative capability makes this area quite challenging. Rapid preliminary screening of biological samples for possible drugs or poisons can be accomplished by radioimmunoassav (RIA) and enzvme-activated immunoassay (EMI'P) i ~ i g 4). . These techniques are based upon the specificity of the antibody-antigen complex. RIA involves the
44
Journal of Chemical Education
Forensic Chemistry is a very exciting and challenging field of applied chemistry. Students interested in this field should pursue a bachelor degree in chemistry with either a second major in biology or a minor in biology. Some specialization in the field of forensic science is possible at the BS level, but this should not he done a t the expense of the basics in both chemistry and biology. Specialization is more desirable at the masters or doctoral level. Literature Cited Gaensslen. R.E., Low Enlorcement Communications. 23 (February19801. Camp, MichaelJ., A n d y . Chem., 52,422 A (19801. Bziner. R C.et al. "Determination of Antimony, Lead, and Copper from Hand Swabs by Anodic Stripping Voltamm~tw: American Academy of Forensic Science 32nd Annual Meeting, New Orleans, La.. February 1980,Abstract p. 48. Williams, R. L., Chem in Australia, 41.79 (1980). Grsdy. Denise, "Blood WiUTell?Discouer, 38 (Nouember 1980). Cherry. L s
