Forensic Toxicology in Postmortem Investigations

Transcription

1 Forensic Toxicology in Postmortem Investigations Tech Com: Toxicology by Alphonse Poklis, Ph.D., D.A.B.F.T. Simply stated, toxicology is the study of poisons and concentrates on the chemical and physical properties of toxic substances. The 16th century physician, Paracelsus, suggested that: "All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy." Today, toxicology has been expanded to include a diverse range of interests including evaluation of the risks involved in the use of food additives, pesticides and cosmetics, and studies concerned with occupational poisonings, environmental pollut i o n, the effects of radiation, and biological and chemical warfare. However, it is the forensic toxicologist w h o has held the title of toxicologist for the longest period of time. The complete investigation of the cause or causes of sudden death is an important civic responsibility. Establishing the cause of death rests with the medical examiner, coroner or pathologist, but success in arriving at the correct conclusion frequently is dependent upon the combined efforts of the pathologist and the toxicologist. The cause of death in cases of poisoning cannot be proven beyond contention without toxicologic analysis which establishes the presence of the toxicant in the tissues and body fluids of the deceased. Many drugs or poisons do not produce any characteristic pathologic lesions, and their presence in the body can be demonstrated only by chemical methods of isolation and identification. If toxicologic analyses are avoided, deaths due to poisoning may be erroneously ascribed to some entirely different cause, or poisonings may be designated as the cause of death w i t h o u t any definite proof. Such erroneous diagnoses may have significant legal and social consequences as illustrated by the following cases. Alphonse Poklis, Ph.D., D.A.B.F.T., is Assistant Professor in Forensic and Environmental Toxicology, Department of Pathology, at St. Louis University School of Medicine, St. Louis, Missouri. 224 Case 1 A man was f o u n d dead in bed w i t h an e m p t y pint bottle of l i q u i d p h e n o l next to h i m. Corrosive burns were noticed on the face, a r o u n d the m o u t h and on the hands. It was assumed that death was due to suicidal ingestion of p h e n o l. Toxicologic analysis demonstrated the presence of a large a m o u n t of p h e n o l in the s t o m a c h ; however, the brain, b l o o d and liver analyses gave negative results, indicating that the poison had been administered after the man was dead. Subsequent investigation revealed that the man's wife had a secret lover. The lover had suffocated the husband w i t h a p i l l o w ; t h e n lover and w i f e, w i t h the aid of the t u b i n g f r o m an enema bag, had p o u r e d the p h e n o l d o w n the esophagus and into the stomach of the dead m a n. ' Case 2 A policeman patroling the waterfront noticed a man w i t h a large b u n d l e, about to t h r o w it into the river. U p o n o p e n i n g the b u n d l e, the officer discovered the torso of a w o m a n. The head, arms and legs were missing. They w e r e discovered d u r i n g the next few days in various parts of the city. The man was held for q u e s t i o n i n g at the district police station. The suspect t o l d the f o l l o w i n g story: The w o m a n was his c o m m o n - l a w w i f e. They had been d r i n k i n g and had q u a r r e l e d. He then left the house. O n returning the next m o r n i n g, he f o u n d his wife dead on the floor. He was afraid that the police w o u l d charge him w i t h m u r d e r, so he d i s m e m b e r e d her and was attempting to dispose of the remains w h e n the officer a p p r e h e n d e d h i m. M e a n w h i l e, neighbors living in the same house discovered that illuminating gas was c o m i n g f r o m the r o o m in w h i c h the t w o lived. Investigation disclosed that a coffee pot on the gas stove had boiled over, p u t t i n g out the gas flame. The gas filled the r o o m. Toxicologic analyses of the wife's b l o o d gave a 63% carbon m o n o x i d e saturation, and analysis of the brain showed an ethanol concentration of 0.35% indicating alcohol intoxication. The man was evidently telling the t r u t h. The w o m a n was intoxicated, and in trying to make some coffee, had not noticed that it had boiled over and extinguished the flame. She was then o v e r c o m e by carbon m o n o x i d e and collapsed. The man was cleared of the m u r d e r charge but was held for d i s m e m b e r i n g a h u m a n body. 2 Often the toxicologist is able to furnish valuable evidence concerning the circumstances surrounding a death by demonstrating the presence of ethanol in victims of automotive or industrial accidents, or the presence of carbon monoxide in fire victims. The degree of carbon monoxide saturation of the blood /79/0400/224 $00.75 American Society of Clinical Pathologists

2 may indicate whether the deceased died as a result of the burns or was dead before the fire started, since arson is c o m m o n l y used to conceal homicide. A poorly understood exception to this rule are the victims of flash fires. 3 Licit or illicit psychoactive drugs also can play a significant role in the circumstances associated w i t h sudden or violent death. At times, a negative toxicologic finding is of particular importance in assessing the cause of death, as in the next case. Case 3 A man living in a small t o w n o n the border of one state had an illegitimate son by a w o m a n w h o lived in the a d j o i n i n g state. The w o m a n ' s m o t h e r requested that the man marry her daughter or at least support the c h i l d. He agreed to support the child and left w i t h the baby. T w o weeks later the baby was f o u n d floating in a nearby river. The man was taken into custody, and w h e n questioned he admitted that he killed the c h i l d. He stated that he had put the infant into a bag containing rags soaked w i t h c h l o r o f o r m, placed the sack in the back of his vehicle and driven toward his h o m e across the state border. He said he d i d not k n o w w h e n the child actually d i e d. The man was well versed in matters of criminal law, for a defendant must be tried in the state w h e r e the m u r d e r is c o m m i t t e d. An autopsy was p e r f o r m e d and the organs sent to a toxicologist. No c h l o r o f o r m was detected in any of the organs. Particular attention was given to the brain since this organ absorbs most readily and w o u l d retain, for many months after d e a t h, any c h l o r o f o r m that may have been administered. Marks of violence were f o u n d on the neck and face of the c h i l d. C o n f r o n t e d by this evidence the man admitted that he killed the baby by strangulation and t o l d w h e r e he c o m m i t t e d the murder. 2 Investigation Prior to Analysis Before starting a toxicologic analysis, the toxicologist should have the following i n f o r m a t i o n : age, sex and weight of the deceased; the approximate time of ingestion or exposure to the toxicant; prior drug use by the deceased; and, if applicable, any symptoms displayed prior to death or medications administered by professional personnel d u r i n g treatment for the intoxication. It should be kept in mind that unless empty prescription vials or containers of toxic material are f o u n d in close proximity to the patient, clinical symptoms prior to death are seldom indicative of intoxication. A recent review of clinical impressions of intoxicated patients compared to laboratory findings revealed that in only 59%of the cases, were the drugs suspected f o u n d. 4 In 35% of these cases, additional drugs were present. In 39% of the cases, drugs other than those suspected of inducing the observed intoxication were present. In only 2% of the cases were drugs or toxicants not detected. It must also be kept in mind that illicit drug preparations are notorious for containing ingredients other than those they are reputed to contain. Many powders or preparations sold as mescaline or crystalline tetrahydrocannabinol (THC) are generally f o u n d to be lysergic acid diethylamide (LSD) or phencyclidine (PCP). The latter, PCP, has played an increasingly significant role in automotive accidents and has caused a number of deaths due to fatal intoxications. The recent death of a young man in the metropolitan St. Louis area as a result of fatal intoxication with a rare hallucinogenic amphetamine derivative, methylenedioxyamphetamine (MDA), d e m o n strates the dangers of misrepresentation in the illicit drug market. The victim believed he was ingesting a mixture of LSD, morphine and amphetamine. If not consumed in large doses, it is doubtful that ingestion of this mixture w o u l d have led to a fatal outcome. Prior knowledge of medically administered drugs can save the toxicology laboratory a great deal of t i m e, effort and expense, as exemplified in the following case. Case 4 A man r e t u r n i n g f r o m a business trip discovered his w i f e in bed w i t h another man. A quarrel broke out between the t w o m e n, and although the exact sequence of events is u n k n o w n, the husband shot the o t h e r man. The wife's lover was reported t o be a f r e q u e n t user of cocaine. W h e t h e r or not he was under the influence of the d r u g at the time of the shooting was to be a significant factor in the legal p r o c e e d i n g of the case. The initial analysis of the fluids and tissues of the deceased failed to disclose the presence of cocaine; however, lidocaine was detected in the b l o o d. O f t e n other local anesthetics such as procaine or lidocaine are used to " c u t " illicit cocaine. As a result of this f i n d i n g, all analyses were repeated w i t h the utmost care. Again negative results for cocaine or benzoylecgonine w e r e o b t a i n e d. Later it was learned that the lidocaine had been administered in the emergency r o o m of a local hospital just prior to the man's death. Specimens and their Collection Probably no other area causes as much disturbance to the smooth w o r k i n g relationship between the pathologist and toxicologist as the type and quantity of specimen collected and submitted for analysis. Often the quality and quantity of such specimens vary tremendously in similar cases. In a medical examiner's office where autopsies and toxologic testing are performed in the same building, problems of this nature can be dealt with easily. However, there seems to be an inverse relationship between the quality of specimens and the distance between the autopsy and the laboratory, which often cripples the effectiveness of state coroner or medical examiner systems where specimens are sent to a central laboratory for examination. An all too c o m m o n request to "examine for the presence of all drugs and poisons" when only 10 ml of blood is supplied is an unreasonable request, usually the result of poor communication between the pathologist and toxicologist. The only solution to this LABORATORY M E D I C I N E VOL. 10, NO. 4, APRIL

3 problem revolves around more effective and extensive communication between the parties involved. The need for diversity in sources of sample collection (blood, urine, bile, liver, brain) is due to toxicokinetic factors. Drugs and other toxicants display varying affinities for body tissues and fluids. This renders some specimens particularly useful for the detection of certain toxicants while other specimens may be of no value. After an injection of heroin, the drug is rapidly biotransformed to morphine which clears the blood rapidly, is conjugated in the liver and rapidly excreted in the bile. Small amounts of both free and conjugated morphine may be excreted in the urine. Therefore, blood is of little value in postmortem screening procedures to determine morphine or heroin use. Urine may be useful, but bile is certainly the specimen of choice. Case 5 Two y o u n g men burglarized a veterinarian's office and stole many medicinal preparations. The next evening one of the men was f o u n d dead in a motel r o o m. The body was sitting in a chair, vomit covered the front of the deceased, and on the floor next to the chair was an empty syringe and a half-empty vial of Innovar V e t " ". Innovar"", an intravenous anesthetic, contains a mixture of fentanyl and d r o p e r i d o l. The veterinary product contains about 20 times the dose per milliliter than that used in human surgical procedures. No autopsy was p e r f o r m e d. The coroner sent the f o l l o w i n g items to the state toxicology laborat o r y : the vial of Innovar V e t " ", v o m i t, t w o milliliters of b l o o d, and all clothes f r o m the deceased, as well as several empty bottles of soft drinks, a half-empty bottle of whiskey, a sleeping bag, several o p e n e d bags of snack f o o d and a glass f r o m the motel r o o m. Because of an insufficient quantity of body fluid samples, the laboratory was able to establish only that the vial contained Innovar V e t " " and that the deceased contained no detectable amount of a l c o h o l. A large quantity of sample is necessary for thorough toxicologic analysis, because a procedure which extracts or identifies one c o m p o u n d or class of compounds may be ineffective in extracting or identifying another. An appreciation of this problem may be obtained by briefly reviewing the toxicologic approach to the analysis of the liver in the "general u n k n o w n " case. There are generally five major methods of drug extraction from liver specimens: 1) Stas-Otto, 2) tungstic acid, 3) ammonium sulfate, 4) acid digestion, and 5) direct extraction. The Stas-Otto method was developed before the turn of the century and is based on the ability of acidified ethanol to precipitate protein and simultaneously dissolve or extract alkaloidal poisons. The method produces good recoveries of basic drugs (e.g., quinine, codeine, strychnine), but recoveries of acidic drugs such as barbiturates are very poor. The procedure takes several days to produce a final extract. 226 LABORATORY MEDICINE VOL. 10. NO. 4. APRIL 1979 The tungstic acid and direct extraction methods are useful for barbiturate analysis, but the yield of many basic drugs (e.g., imipramine, amitriptyline) is poor. Direct extraction is particularly unsuited for extracting drugs which form conjugated metabolites such as morphine, amitriptyline and phenylbutazone. A m m o n i u m sulfate may be effective for the extraction of basic drugs but is not applicable to the analysis of barbiturates or other acidic drugs. Acid digestion is excellent for the extraction of protein-bound or conjugated drugs, such as phenothiazines, imipramine, quinine and m o r p h i n e ; however, the method causes hydrolysis or decomposition of many other drugs, such as cocaine, belladonna alkaloids, benzodiazepines and propoxyphene. Each of these methods must also be evaluated for the propensity of the extracting solvents to form emulsions with tissue components, the amount of natural body constituents co-extracted with the toxicant, and other physical and chemical parameters. Hence, the toxicologist must use a complex and often time-consuming approach to what seems at first glance a simple p r o b l e m : removal of drugs from the liver. The pathologist w h o performs the medicolegal autopsy has the primary responsibility for the collection and preservation of proper samples for toxicologic analysis. Specimens necessary for complete toxicologic analysis are presented in Table I. In certain instances, additional specimens may be needed, such as hair or bone in suspected chronic poisoning from metallic compounds. Each individual specimen should be placed in a separate container. Glass jars with screw tops (Mason jars) are most useful for tissue, although sealed plastic bags are acceptable. Specimens should be taken prior to embalming, as this process may destroy or dilute the toxicants present and render their detection impossible. While many toxicants may be detectable in embalmed tissue, evaluation of the quantitative results of analysis is difficult or impossible. Sodium fluoride should be added to one tube of blood intended for the analysis of ethanol, carbon monoxide and sugars. No preservative should be added to the tissue specimens. Blood and urine samples should be kept refrigerated and tissue specimens frozen. If the specimens are to be transported over a considerable distance to the laboratory, they should be packaged with dry ice. If not shipped in dry ice, the putrefication of the samples may greatly hinder the toxicologic analysis. The pathologist should label each container and the identification should bear the date and time of

4 autopsy, the name of the decedent, the identity of the sample and the signature of the pathologist. It is imperative that an adequate chain of custody of the specimens submitted to the laboratory is maintained. In most jurisdictions, blood is the sample commonly chosen for analysis in legal medical cases, particularly for ethanol determinations. If no autopsy is performed, blood is often obtained from the heart by puncturing the chest wall with a long needle. Erroneously high ethanol levels may result from this manner of sample collection if the needle nicks the esophagus or if internal injury has ruptured the stomach and diaphragm, resulting in a bathing of the thoracic cavity with gastric contents. When no autopsy is performed, blood drawn from the femoral vein or cerebrospinal fluid taken from the cisterna magna is preferable. At autopsy, blood is usually obtained from the heart. The heart should be gently massaged before taking the sample in order to promote mixing of the blood in the chambers. A high or low hematocrit may lead t o erroneously high or low ethanol results. Ethanol is distributed in the body according to the water content of the tissues and fluids. Therefore, plasma contains about 10% more ethanol than whole b l o o d. In cases of suspected ethanol intoxication, the brain may be considered preferable to blood for analysis since there is less chance of contamination, and the physiological effects of ethanol are due to its action on the central nervous system. Source of Misunderstanding A major source of misunderstanding about the toxicologists' specimen needs is related to the advances in instrumentation and automation in the routine clinical chemistry laboratory. A physician may submit several milliliters of serum t o the clinical laboratory and within a few hours have the results of a dozen analyses. This is often not the case in postmortem toxicology. It must be remembered that the clinical chemist is analyzing for naturally occurring compounds known to be present, usually in high concentrations. Many of these analyses involve the measurement of enzyme activity which requires only minute specimen quantities. The procedures are generally automated, specific and easy t o perform. However, there are no such automated, specific procedures for identifying or accurately differentiating the thousands of drugs or toxicants which may cause or contribute to death. Toxic levels of toxicants in postmortem specimens may be extremely l o w ; this may be due to the high degree of toxicity of some compounds or the biotransformation of toxicants which d o not cause death i m mediately and are metabolized before the termination of life occurs. Thus the toxicologist must have Table I Specimens Necessary in Cases Requiring A Complete Toxicologic Analysis 1. Blood Samples: Preferably two separate samples should be submitted. a. Sample with no preservative: about 100 milliliters (3 oz). b. Sample with preservative (sodium fluoride): oneortwo tubes (15 milliliters) for alcohol and carbon monoxide. 2 Urine Sample a. One tube with preservative (sodium fluoride). b. The total remaining urine with no preservative. 3 Stomach and Contents 4. Liver Sample: about one half to two thirds of the total weight. 5. Bile Sample: complete amount available. 6. Brain Sample: about one half of the total weight. 7. Kidney Sample: one whole organ. 8. Sample of wash water used to rinse the containers (homicides). 9. Miscellaneous: Other tissues which may be available (cerebrospinal fluid, lung, heart, spleen, vitreous humor). an understanding of the chemical basis of the procedures used to perform toxicologic analyses. Use of Toxicology Results To best utilize the results of toxicologic analysis, the pathologist should familiarize himself with the capabilities of the toxicology laboratory. While the pathologist is knowledgable concerning the meaning of the results of toxicologic analysis for barbiturates, carbon monoxide, ethanol and other c o m m o n toxicants, he may find the toxicologist a valuable information source on less frequently encountered toxicants, and time-exposure or dose-tissue level relationships. In 1975, the American Board of Forensic Toxicology was created t o examine and certify forensic toxicologists. O n e of the stated objectives of the board is " t o make available t o the judicial system, and other publics, a practical and equitable system for readily identifying those persons professing to be specialists in forensic toxicology w h o possess the requisite qualifications and competence." Thus the concerned pathologist may assess the toxicologist's qualifications by inquiring about the toxicologist's certifications. It is imperative that postmortem toxicologic analyses be performed or directly supervised by qualified forensic toxicologists, since the pathologist's evaluation and final diagnosis may be d o m i nated by the toxicology report. Too often, important and complicated analyses are performed by laboratory technicians or qualified chemists with little, if any, understanding of the problems associated with forensic toxicology. LABORATORY MEDICINE VOL. 10, NO. 4, APRIL

5 Case 6 The body of a y o u n g soldier, reported A W O L, was discovered in a d e c o m p o s e d c o n d i t i o n beneath a b u i l d i n g. The tissues were sent to an "analyst" w h o reported that they contained a large amount of a m p h e t a m i n e. The analyst had p e r f o r m e d a BeyerSkinner chemical test and recorded an ultraviolet spectrum of a basic extract. These tests were the basis of his " i d e n t i f i c a t i o n of a m p h e t a m i n e. " The pathologist, f r o m this f i n d i n g, suggested amphetamine poisoning as the cause of death. O n the basis of this report, an intensive investigation was started to d e t e r m i n e h o w the deceased obtained the d r u g and w h e t h e r or not he was a k n o w n a m p h e t a m i n e user. M e a n w h i l e, portions of the tissue were properly analyzed by a toxicologist w h o identified the " a m p h e t a m i n e " as phenylethylamine, a c o m m o n c o m p o n e n t of putrefied tissue. The b o d y of the dead man, in fact, contained no drugs. Phenylethylamine, f o r m e d d u r i n g d e c o m p o s i t i o n by decarboxylat i o n of phenylalanine, gives a positive Beyer-Skinner reaction and has the same ultraviolet spectrum as amphetamine. 5 The pathologist should also inquire as to the general "detection limits" of the procedures used in the laboratory. The analytical methods used in toxicology often vary between laboratories and will greatly influence the reported results. A laboratory using electron-capture gas chromatography as a screening procedure for benzodiazepines will detect "therapeutic levels" of this drug in many cases. However, a laboratory analyzing for the same compounds by ultraviolet spectrophotometry will detect only potentially toxic levels. This variance in analytical capability has a direct effect on the reported involvement of drugs or toxicants in a sudden death. For example, using the laboratories above and a case involving co-ingestion of alcohol and diazepam, the former laboratory w o u l d report concentrations of diazepam, nordiazepam and other metabolites. The latter laboratory w o u l d only report diazepam levels. The spectrophotometric method used by the latter w o u l d have measured the parent drug and all its metabolites as diazepam. Hence, the diazepam level obtained from the first laboratory w o u l d be much lower than that obtained from the second laboratory. Therefore, it is imperative to consider the " m e t h o d o l o g y factor" before interpreting the toxicology results. Summary The success or failure of the forensic toxicologist in detecting toxicants which may have contributed to death is often dependent not only on his own abilities, but on the completeness of the investigation of the circumstances of death and the specimens which are p r o v i d e d. A l t h o u g h the forensic toxicologist often works w i t h the dead, he stands in service to the living. References 1. Freimuth, H.C., Personal Communication. 2. Gettler, A.O., The Historical Development of Toxicology. J, Forens. Sci. 1:3. 3. Hirsch. C S. et al., Carboxyhemoglobin Concentrations in Flash Fire Victims. Am. J. Clin. Pathol. 68: Teitelbaum, D.T., et al Nonconcordance between Clinical Impression and Laboratory Findings in Clinical Toxicology. Clin. Toxicol. 10: Goldbaum. L.R., et al., The Practice of Identification in Analytical Toxicology. J. Forens. Sci. 8:286. r- Tech Talk ADD TO YOUR PRODUCT KNOWLEDGE Use the LABORATORY MEDICINE PDQ Reader Service to request additional information from LM advertisers. Make it a point to check every issue carefully use the Reader Service to request new data, to keep your ready supply of product information up-to-date LABORATORY MEDICINE VOL. 10, NO. 4, APRIL 1979 IS IT oft IS THftr MY /MflGllOflTlONl COULTER. CouuTsn. SMIRKING rtr