1: Introduction to Forensic Toxicology and the Value of a Nationwide Database
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Published:14 Jul 2016
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Special Collection: RSC eTextbook CollectionProduct Type: Textbooks
A. W. Jones, in Forensic Toxicology: Drug Use and Misuse, ed. S. Davies, A. Johnston, and D. Holt, The Royal Society of Chemistry, 2016, pp. 1-29.
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The creation of a nationwide forensic toxicology database (TOXBASE) furnishes a way to monitor trends and patterns of drug abuse in society, including the emergence of new designer drugs and their potential for toxicity. The demographics of people arrested for various drug-related crimes, such as drug-impaired driving, victims of drug-facilitated sexual assault (DFSA), etc., are also available by searching the database. One section of the database is devoted to the drugs encountered in post-mortem toxicology and their involvement in fatal poisonings and the potential for adverse drug–drug interactions. This chapter presents examples of some of the research projects undertaken with the help of a national forensic toxicology database available in Sweden.
1.1 Introduction
Forensic toxicology, formerly known as forensic chemistry, is a multidisciplinary subject concerned with various aspects of chemistry, physiology, pharmacology and toxicology, as well as other branches of science and technology.1,2 Forensic toxicology practitioners are first and foremost trained in analytical chemistry because their principal task is extraction, detection, identification and quantitative analysis of a plethora of drugs and poisons in biological specimens.3,4 Another important duty of the forensic toxicologist or forensic pharmacologist is to provide expert testimony in criminal and civil cases involving the use and abuse of drugs in society and also in drug-related crimes, such as when drunk and drugged drivers are prosecuted.5
Knowledge about the disposition and fate of drugs in the body and how psychoactive substances alter normal functioning of the brain are important considerations when forensic toxicologists interpret their analytical findings in a legal context.6 The relationships between the various clinical signs and symptoms of impairment and the concentrations of psychoactive substances in blood is other relevant information available from TOXBASE, a forensic toxicology database.
The various sub-disciplines of forensic toxicology and the types of information stored in TOXBASE are listed below:
Unnatural death investigations involving poisoning and overdosing with drugs.
Driving under the influence of alcohol and/or other drugs.
Drug facilitated crimes (incapacitation), such as date-rape.
Control of illicit drugs in society, especially by people detained in prisons and other sectors of the criminal justice system.
Child welfare and custody cases where suspicion arises that the parents or care-givers abuse drugs or administer drugs to the infants or elderly for which they are responsible.
Monitoring the use of banned drugs by people enrolled in treatment and rehabilitation programs for substance abuse disorder.
Drug testing in the workplace.
Use of doping agents in sports.
Forensic pharmacovigilance is a subject of increasing interest and importance when it comes to the safety of medicines and the dangers of prescribing certain combinations of drugs to patients.7,8 The information in TOXBASE can help to flag for the emergence of new recreational drugs of abuse (designer drugs), and help to decide whether these should be banned or classified as controlled substances. Other information stored in TOXBASE deals with the drugs commonly encountered in poisoning deaths.9,10 By cross-linking information in TOXBASE with other databases (e.g. prescription registers) or safety of medicines records the potential dangers of certain drugs and drug combinations become easier to document.11 The post-mortem section of TOXBASE can be complemented with information about the cause and manner of death (e.g. suicide, homicide, accident) according to findings at autopsy and the official death certificate.12
1.2 Forensic Toxicology in Sweden
Geographically, Sweden is roughly the same size as California or twice the size of the UK. However, the population of Sweden is only 9.5 million (2014), which means that one central forensic toxicology laboratory provides analytical services for the whole country. This centralization has several advantages when it comes to the choice of analytical methods and the availability of modern state-of-the-art equipment, quality assurance procedures and laboratory accreditation.
The annual workload in terms of numbers and types of forensic cases submitted for analysis to the Swedish National Laboratory of Forensic Toxicology are summarized in Table 1.1. Official records show that the number of forensic autopsies has remained remarkably constant, averaging 5000 per year over the past 20 years. The laboratory workload is strongly influenced by new government legislation dealing with abuse of alcohol and drugs in society, as exemplified by enactment of a zero-tolerance law for driving under the influence of drugs (DUID) in 1999.13 The forensic toxicology database available in Sweden contains information about hundreds of drugs and their metabolites and the concentrations in blood and other biological specimens from living and deceased persons.14 Senior scientists at the Swedish National Laboratory of Forensic Toxicology are closely associated with the faculty of medicine at the University of Linköping, particularly clinical pharmacology. A good collaboration between these two organizations has resulted in considerable research activity and many joint publications.15
Number and type of cases submitted to the Swedish Board of Forensic Medicine for toxicological analysis during the years 2012, 2013 and 2014.
Type of investigation . | Year 2012 . | Year 2013 . | Year 2014 . |
---|---|---|---|
Post-mortem toxicology | 5051 | 5084 | 5310 |
Traffic cases (drunk and drugged drivers)a | 14 867 | 14 769 | 16 037 |
Abuse of illicit drugs in the community | 38 119 | 37 860 | 37 426 |
Abuse of illicit drugs by prison inmates | 29 105 | 24 819 | 25 709 |
Sexual assault cases that might involve drugs | 1531 | 1377 | 1565 |
Patients and others in drug rehabilitation programs | 7100 | 7656 | 8991 |
Type of investigation . | Year 2012 . | Year 2013 . | Year 2014 . |
---|---|---|---|
Post-mortem toxicology | 5051 | 5084 | 5310 |
Traffic cases (drunk and drugged drivers)a | 14 867 | 14 769 | 16 037 |
Abuse of illicit drugs in the community | 38 119 | 37 860 | 37 426 |
Abuse of illicit drugs by prison inmates | 29 105 | 24 819 | 25 709 |
Sexual assault cases that might involve drugs | 1531 | 1377 | 1565 |
Patients and others in drug rehabilitation programs | 7100 | 7656 | 8991 |
Arrested drivers submitting to an evidential breath-alcohol test are not included in this table.
Forensic autopsies in Sweden are carried out at the six university teaching hospitals, which are located in the cities of Umeå, Uppsala, Stockholm, Gothenburg, Linköping and Lund. During an autopsy, the forensic pathologists take blood and other biological specimens for toxicological analysis. The preferred source of blood is from a femoral vein and, in addition, specimens of urine and eye fluid (vitreous humor) are taken and sent for analysis of drugs and poisons.
The sampling of biological specimens is done in a highly standardized way and chemical preservatives such as sodium or potassium fluoride (1–2%) are added as enzyme inhibitor to stabilize drug concentrations after sampling. If blood from a femoral vein is not available, owing to massive trauma or decomposition of the body, then cardiac blood is usually sent for toxicological analysis. The biological specimens are shipped to the central forensic toxicology laboratory by special delivery and are refrigerated during transport and storage. The results of the toxicological analysis are of prime importance when unnatural deaths are investigated and when the anatomical and histological evidence fails to reveal the cause and manner of death.16
Figure 1.1 is a flow chart showing the forensic toxicology routines operational when nothing remarkable was discovered after performing the autopsy. A negative or inconclusive autopsy shifts attention towards poisoning as a possible cause of death, which requires a close collaboration and discussion between the pathologist and the toxicologist.17 Witness statements and discoveries made by the police authorities at the death scene, especially any drugs or drug paraphernalia found near the body, is other important information. Likewise, interviews with relatives and friends about the deceased's alcohol and/or drug habits and general state of health is other relevant information to consider when poisoning deaths are investigated.
Flow diagram of the forensic toxicology routines during investigations of suspicious deaths when nothing remarkable was found at autopsy.
Flow diagram of the forensic toxicology routines during investigations of suspicious deaths when nothing remarkable was found at autopsy.
1.3 Analytical Methods
Forensic toxicology is essentially analytical chemistry applied to the determination of drugs and toxins in biological specimens.4,18,19 The accuracy, precision and specificity of the methods used, including limit of detection (LOD) and limit of quantitation (LOQ), are important to document. In this connection, one needs to differentiate between a drug screening analysis and a more sophisticated verification and quantitative analysis of a particular drug.20 Traditionally, the preliminary screening analysis involves some type of enzyme immunoassay procedure, which is generally targeted towards groups of drugs rather than individual substances.21 Typical drug categories encountered in forensic toxicology include opiates, cannabinoids, amphetamines, cocaine metabolites and benzodiazepines. The objective of the screening test is to eliminate “drug negative” cases from further consideration and to identify presumptive positive cases. More modern approaches to drug screening involve some type of hyphenated technique such as liquid chromatography (LC) or gas chromatography (GC) combined with time-of-flight (TOF) mass spectrometry (MS) or LC-TOF-MS, which is now used routinely in many laboratories.22–24
Urine is the preferred biological specimen for screening analysis of drugs and their metabolites, because concentrations excreted in the urine are higher than in the blood.25 Furthermore, drugs and metabolites are excreted for a longer time in the urine, which lengthens the window of detection considerably.26 If urine is unavailable, then screening analysis of drugs is done on a blood sample after precipitation of the proteins. When immunoassay methods are used, the choice of analytical cut-off concentrations become important because these influence the proportion of false positives and false negatives after a verification analysis is done.27
Another useful biological matrix gaining ground in forensic toxicology and widely used for analysis of drugs and toxins is hair strands (also see Chapter 20).28,29 Depending on the rate of growth of the hair, this biological matrix can detect the intake of drugs spanning back weeks or months.30 By means of segmental analysis of the hair strands this furnishes an approximate timeline reflecting exposure to drugs, which is helpful to verify or challenge compliance with prescribed medication.31 Hair is viable as a specimen for drug analysis even if the body is decomposed and when other specimens might not be available or unsuitable for toxicological analysis.32 Another unusual matrix used in toxicology is finger or toe nail clippings (also see Chapter 19), which can be taken from exhumed bodies and the analytical results furnish information about drug intake during life.33
The verification methods used in forensic toxicology laboratories generally involve a four-step procedure:
Use of liquid–liquid or solid-phase extraction to “clean up” the sample and extract drugs and metabolites for further analysis.
After extraction into an organic solvent, the parent drugs and metabolites are separated by use of some type of gas or liquid chromatography technique.
Qualitative identification is achieved based on GC retention times or by running a mass spectrum and then comparing the data with known authentic substances or libraries of known compounds.
Quantitative analysis of the amount of substance present is obtained from the response of one or more detectors, either flame ionization, nitrogen–phosphorus, electron-capture or a mass selective detector.34
If verification analysis shows concentrations of drugs above the method LOQ, then descriptive statistics (mean, median and upper percentiles) can be justifiably calculated and entered into the database for future reference.35 During statistical analysis of data, because drug concentrations in blood tend to be skewed to the right, the median of the frequency distribution is a better indication of the central tendency than the mean value.
1.4 Post-mortem Toxicology
In post-mortem (PM) toxicology the condition of the specimen received for analysis is highly variable, depending on the circumstances surrounding the death (e.g. extensive trauma and blood loss) and whether the body was decomposed, which might impact on the concentrations of certain drugs present.36 Pre-analytical sources of variation tend to dominate over analytical sources of variation, as outlined in a recent review article37 and by analysis of methadone in blood from different sampling sites.38 Some practitioners advocate that toxicology results should be reported as the concentration of drug or toxin in the specimen as received, whether blood, urine or vitreous humor.
The word autopsy means to see for oneself and entails making an external and internal examining of a corpse to discover the cause of death.39 During an autopsy the pathologist has to document any anatomical, pathological or medical conditions that might account for the person's sudden and unexpected death. Most practitioners make use of the well-proven triad of autopsy findings (including histopathology), discoveries at the scene, and toxicological analysis of alcohol and/or other drugs in blood samples.40 The known drinking and/or drug habits of the deceased is obviously relevant when intoxication deaths are considered.
Forensic autopsies are usually requested by the police authorities when a suspicious out-of-hospital death is investigated. The coroner or medical examiner is charged with assembling all available evidence before issuing a death certificate in which the cause and manner of death is reported or simply given as unascertained.41 Deaths caused by overdosing with drugs, either accidentally or intentionally in a suicide attempt, rarely leave tell-tale signs for the pathologist, although froth in the mouth and airways is a characteristic of heroin or opioid-related deaths.42
A poisoning death might be the result of suicide, homicide or an accidental (unintentional) overdose with drugs and is not always easy to determine, hence “inconclusive”, “uncertain” or “undetermined” often appear on death certificates.43 The concentrations of drugs in blood are of prime importance when intoxication deaths are investigated, because these give the best indication of the effects on vital body functions, such as respiratory and circulatory centers in the brain.
Poly-drug use (at least five different medications) is increasingly common in today's society, especially in the elderly, and use of multiple drugs increases the propensity for fatal drug–drug interactions.44 The physiological changes that occur during ageing, including renal and hepatic functioning, body composition and gastric emptying, also impact on uptake, distribution, metabolism and excretion of drugs that deserve consideration when toxicology results are interpreted.45 Many practitioners find it useful to compare the post-mortem concentrations of drugs with concentrations encountered during therapeutic drug monitoring (TDM). However, such comparisons are complicated for various reasons, such as the composition of post-mortem blood (sometimes clotted) and the fact that TDM analysis is usually done on specimens of plasma or serum, which tend to contain higher drug concentrations compared with whole blood.46
The concentrations of drugs in post-mortem blood should not be converted into the dose of drug a person might have ingested during life based on body weight and the drug's volume of distribution.47 The phenomenon of post-mortem redistribution of drugs refers to time-dependent changes in concentration in blood after death and before samples are time-dependent taken at autopsy. The magnitude of this redistribution phenomenon seems to differ for different drugs, depending on lipid solubility, tissue uptake, distribution volume and other properties.41,48
Table 1.2 shows descriptive statistics for the concentrations of 20 drugs most often identified in femoral blood in connection with forensic autopsies in Sweden and Finland.35,49 Both these nations use highly standardized routines for sampling femoral blood for toxicological analysis and modern and comparable analytical methods are used.
Descriptive statistics of the concentrations of the 20 drugs most often identified in post-mortem femoral blood in all causes of death. A comparison is made for TOXBASES available in Finland and Sweden.
Drugs identified in femoral blood . | Country . | Number of cases (N) . | LOQ (mg L−1) . | Mean (mg L−1) . | Median (mg L−1) . | Upper percentiles (mg L−1) . | ||
---|---|---|---|---|---|---|---|---|
90th . | 95th . | 97.5th . | ||||||
Alprazolam | Sweden | 716 | 0.02 | 0.09 | 0.06 | 0.18 | 0.30 | 0.40 |
Finland | 940 | 0.02 | 0.09 | 0.05 | 0.20 | 0.30 | 0.40 | |
Amitriptyline | Sweden | 233 | 0.05 | 0.77 | 0.40 | 2.0 | 2.94 | 3.96 |
Finland | 1589 | 0.10 | 1.5 | 0.40 | 2.9 | 5.5 | 8.8 | |
Amphetamine | Sweden | 558 | 0.03 | 1.54 | 0.5 | 2.9 | 4.5 | 6.3 |
Finland | 565 | 0.04 | 0.91 | 0.28 | 2.1 | 3.7 | 6.2 | |
Carbamazepine | Sweden | 566 | 0.5 | 6.4 | 4.8 | 12 | 15 | 20 |
Finland | 1482 | 0.3 | 7.9 | 6.2 | 13 | 19 | 27 | |
Citalopram | Sweden | 1302 | 0.05 | 0.72 | 0.40 | 1.1 | 1.7 | 3.75 |
Finland | 3542 | 0.10 | 0.97 | 0.40 | 1.4 | 2.4 | 5.3 | |
Codeine | Sweden | 843 | 0.005 | 0.32 | 0.05 | 0.7 | 1.3 | 2.4 |
Finland | 1903 | 0.02 | 0.72 | 0.16 | 1.8 | 3.2 | 5.1 | |
Dextropropoxyphene | Sweden | 694 | 0.10 | 2.0 | 0.8 | 4.4 | 6.9 | 10.2 |
Finland | 249 | 0.10 | 6.5 | 2.6 | 12.0 | 17.0 | 38.0 | |
Diazepam | Sweden | 1223 | 0.05 | 0.23 | 0.10 | 0.5 | 0.7 | 1.0 |
Finland | 7404 | 0.02 | 0.17 | 0.09 | 0.4 | 0.6 | 0.8 | |
Fluoxetine | Sweden | 193 | 0.10 | 0.63 | 0.30 | 1.58 | 1.94 | 2.64 |
Finland | 649 | 0.20 | 0.80 | 0.50 | 1.60 | 2.50 | 3.60 | |
Hydroxyzine | Sweden | 266 | 0.05 | 0.45 | 0.20 | 0.86 | 1.9 | 3.4 |
Finland | 159 | 0.20 | 0.80 | 0.30 | 1.6 | 2.8 | 5.3 | |
Levomepromazine | Sweden | 242 | 0.05 | 1.02 | 0.2 | 1.2 | 2.9 | 5.5 |
Finland | 1602 | 0.10 | 0.99 | 0.4 | 1.9 | 3.2 | 5.0 | |
Methadone | Sweden | 503 | 0.10 | 0.51 | 0.30 | 1.1 | 1.5 | 1.9 |
Finland | 207 | 0.05 | 0.59 | 0.40 | 1.3 | 1.8 | 2.2 | |
Mirtazapine | Sweden | 659 | 0.05 | 0.34 | 0.1 | 0.6 | 1.1 | 1.8 |
Finland | 2179 | 0.05 | 0.49 | 0.20 | 0.80 | 1.7 | 2.9 | |
Morphine | Sweden | 906 | 0.005 | 0.30 | 0.11 | 0.5 | 0.86 | 1.54 |
Finland | 1094 | 0.02 | 0.20 | 0.07 | 0.37 | 0.67 | 1.1 | |
Sertraline | Sweden | 508 | 0.05 | 0.34 | 0.2 | 0.7 | 1.0 | 1.6 |
Finland | 445 | 0.10 | 0.55 | 0.30 | 1.0 | 1.7 | 2.3 | |
THC (cannabis or marijuana use) | Sweden | 467 | 0.0003 | 0.003 | 0.001 | 0.007 | 0.011 | 0.016 |
Finland | 347 | 0.001 | 0.005 | 0.002 | 0.008 | 0.013 | 0.024 | |
Tramadol | Sweden | 716 | 0.05 | 2.64 | 0.60 | 5.0 | 10.2 | 19.8 |
Finland | 1581 | 0.10 | 3.1 | 0.90 | 6.5 | 13.0 | 21.0 | |
Venlefaxine | Sweden | 451 | 0.05 | 4.0 | 0.4 | 4.1 | 18.5 | 48.5 |
Finland | 824 | 0.10 | 3.7 | 0.6 | 5.7 | 17.0 | 33.0 | |
Zolpidem | Sweden | 417 | 0.05 | 0.60 | 0.20 | 1.6 | 2.8 | 3.6 |
Finland | 287 | 0.10 | 0.59 | 0.30 | 1.4 | 2.0 | 2.9 | |
Zopiclone | Sweden | 994 | 0.02 | 0.30 | 0.09 | 0.7 | 1.3 | 1.9 |
Finland | 2577 | 0.02 | 0.34 | 0.10 | 0.8 | 1.5 | 2.4 |
Drugs identified in femoral blood . | Country . | Number of cases (N) . | LOQ (mg L−1) . | Mean (mg L−1) . | Median (mg L−1) . | Upper percentiles (mg L−1) . | ||
---|---|---|---|---|---|---|---|---|
90th . | 95th . | 97.5th . | ||||||
Alprazolam | Sweden | 716 | 0.02 | 0.09 | 0.06 | 0.18 | 0.30 | 0.40 |
Finland | 940 | 0.02 | 0.09 | 0.05 | 0.20 | 0.30 | 0.40 | |
Amitriptyline | Sweden | 233 | 0.05 | 0.77 | 0.40 | 2.0 | 2.94 | 3.96 |
Finland | 1589 | 0.10 | 1.5 | 0.40 | 2.9 | 5.5 | 8.8 | |
Amphetamine | Sweden | 558 | 0.03 | 1.54 | 0.5 | 2.9 | 4.5 | 6.3 |
Finland | 565 | 0.04 | 0.91 | 0.28 | 2.1 | 3.7 | 6.2 | |
Carbamazepine | Sweden | 566 | 0.5 | 6.4 | 4.8 | 12 | 15 | 20 |
Finland | 1482 | 0.3 | 7.9 | 6.2 | 13 | 19 | 27 | |
Citalopram | Sweden | 1302 | 0.05 | 0.72 | 0.40 | 1.1 | 1.7 | 3.75 |
Finland | 3542 | 0.10 | 0.97 | 0.40 | 1.4 | 2.4 | 5.3 | |
Codeine | Sweden | 843 | 0.005 | 0.32 | 0.05 | 0.7 | 1.3 | 2.4 |
Finland | 1903 | 0.02 | 0.72 | 0.16 | 1.8 | 3.2 | 5.1 | |
Dextropropoxyphene | Sweden | 694 | 0.10 | 2.0 | 0.8 | 4.4 | 6.9 | 10.2 |
Finland | 249 | 0.10 | 6.5 | 2.6 | 12.0 | 17.0 | 38.0 | |
Diazepam | Sweden | 1223 | 0.05 | 0.23 | 0.10 | 0.5 | 0.7 | 1.0 |
Finland | 7404 | 0.02 | 0.17 | 0.09 | 0.4 | 0.6 | 0.8 | |
Fluoxetine | Sweden | 193 | 0.10 | 0.63 | 0.30 | 1.58 | 1.94 | 2.64 |
Finland | 649 | 0.20 | 0.80 | 0.50 | 1.60 | 2.50 | 3.60 | |
Hydroxyzine | Sweden | 266 | 0.05 | 0.45 | 0.20 | 0.86 | 1.9 | 3.4 |
Finland | 159 | 0.20 | 0.80 | 0.30 | 1.6 | 2.8 | 5.3 | |
Levomepromazine | Sweden | 242 | 0.05 | 1.02 | 0.2 | 1.2 | 2.9 | 5.5 |
Finland | 1602 | 0.10 | 0.99 | 0.4 | 1.9 | 3.2 | 5.0 | |
Methadone | Sweden | 503 | 0.10 | 0.51 | 0.30 | 1.1 | 1.5 | 1.9 |
Finland | 207 | 0.05 | 0.59 | 0.40 | 1.3 | 1.8 | 2.2 | |
Mirtazapine | Sweden | 659 | 0.05 | 0.34 | 0.1 | 0.6 | 1.1 | 1.8 |
Finland | 2179 | 0.05 | 0.49 | 0.20 | 0.80 | 1.7 | 2.9 | |
Morphine | Sweden | 906 | 0.005 | 0.30 | 0.11 | 0.5 | 0.86 | 1.54 |
Finland | 1094 | 0.02 | 0.20 | 0.07 | 0.37 | 0.67 | 1.1 | |
Sertraline | Sweden | 508 | 0.05 | 0.34 | 0.2 | 0.7 | 1.0 | 1.6 |
Finland | 445 | 0.10 | 0.55 | 0.30 | 1.0 | 1.7 | 2.3 | |
THC (cannabis or marijuana use) | Sweden | 467 | 0.0003 | 0.003 | 0.001 | 0.007 | 0.011 | 0.016 |
Finland | 347 | 0.001 | 0.005 | 0.002 | 0.008 | 0.013 | 0.024 | |
Tramadol | Sweden | 716 | 0.05 | 2.64 | 0.60 | 5.0 | 10.2 | 19.8 |
Finland | 1581 | 0.10 | 3.1 | 0.90 | 6.5 | 13.0 | 21.0 | |
Venlefaxine | Sweden | 451 | 0.05 | 4.0 | 0.4 | 4.1 | 18.5 | 48.5 |
Finland | 824 | 0.10 | 3.7 | 0.6 | 5.7 | 17.0 | 33.0 | |
Zolpidem | Sweden | 417 | 0.05 | 0.60 | 0.20 | 1.6 | 2.8 | 3.6 |
Finland | 287 | 0.10 | 0.59 | 0.30 | 1.4 | 2.0 | 2.9 | |
Zopiclone | Sweden | 994 | 0.02 | 0.30 | 0.09 | 0.7 | 1.3 | 1.9 |
Finland | 2577 | 0.02 | 0.34 | 0.10 | 0.8 | 1.5 | 2.4 |
The large sample sizes (N) in Table 1.2 make this useful reference data to compare with the drug concentrations reported in individual cases when the same drugs are identified. Note that all-cause mortality was included in the cases reported in Table 1.2 and not just poisoning deaths. A particular problem with interpreting drug concentrations in post-mortem cases is that the deceased seldom used a single drug or medication. The high prevalence of poly-drug use in today's society heightens the risk of encountering a drug-related intoxication death.50 Nevertheless, it is often possible to identify the major drug culprit among several other drugs identified in blood. In Finland, pathologists found that three drugs in particular were over-represented in poisoning deaths and these were dextropropoxyphene (propoxyphene), buprenorphine and methadone, all widely used opioid prescription pain medications, but also drugs subject to abuse.49 This confirms the trends seen in many US states, showing an upsurge of overdose deaths involving prescription pain medication, such as fentanyl, methadone, oxycodone and hydrocodone.51,52 The drug most often identified in mono-intoxication deaths in Sweden was the legal drug ethanol followed by the illicit drug heroin.53
As mentioned earlier, when overdose deaths are interpreted a major problem is site-to-site variation in drug concentrations, which might vary by a factor of 10 for some drugs.54,55 A lot depends on the condition of the body, the degree of trauma, the post-mortem interval, the ambient temperature (refrigeration) and whether decomposition and putrefaction processes had commenced, all of which needs to be noted and made clear when interpretations are made.45,56 The movement of drugs from high concentrations in the stomach contents or sequestered to body organs and tissues into the vascular system after death is appreciated by pathologists and toxicologists and is considered when the analytical results are interpreted.48,57
1.5 Alcohol and Drug Impaired Driving
Drunk and drugged drivers are responsible for many road-traffic crashes and impaired drivers are over-represented among drivers killed in such collisions (also see Chapter 13).58,59 The police authorities throughout Sweden send specimens of blood and urine from apprehended drivers to the National Laboratory of Forensic Toxicology for analysis. TOXBASE therefore contains analytical results from all impaired driving cases, including the demographics of offenders, the types of drugs used and the concentrations in blood. Also available in some cases are signs and/or symptoms of impairment observed by arresting police officers or when a driver was examined by a physician and clinical tests of intoxication were administered.60
Punishable (statutory) limits of blood–alcohol concentration exist in most nations, although these vary four-fold from 20 to 80 mg per 100 mL (0.02–0.08 g%), probably reflecting national politics rather than traffic-safety research.61 Moreover, many countries now enforce zero-tolerance laws for driving under the influence of drugs other than alcohol.58,62 Besides a ban on driving after use of illicit recreational drugs, many psychoactive prescription drugs are included, such as benzodiazepines, because they impair driving ability when taken in overdose and this medication is subject to abuse.63 Information gleaned from the Swedish version of TOXBASE has been used to document the demographics of traffic offenders and the concentrations of drugs (both licit and illicit) determined in blood in arrested drivers and in drivers killed in traffic crashes.60,64
Table 1.3 presents the age and gender of people arrested in Sweden for drunk or drugged driving offences. The results show a clear predominance of male offenders (85–90%) and a relationship between choice of drug and mean age of the individuals. Alcohol impaired drivers were eldest (mean 40 years) and those taking γ-hydroxybutyrate (GHB) were youngest (mean 24 years). The cases selected for display in Table 1.3 were those when only a single drug was present in the blood sample analyzed, even though multiple drugs are a common finding in people arrested for impaired driving in Sweden and other countries.13,65,66
Demographics of people arrested for drug-impaired driving in Sweden and the drugs identified in blood arranged according to mean age of traffic offenders.
Drug present in venous blood samples . | Number of cases . | Men (%) . | Women (%) . | Age of suspects (mean±SD) (years) . |
---|---|---|---|---|
Ethanol | 32 814 | 90% | 10% | 40.0±8.7 |
Amphetamine | 9162 | 85% | 15% | 36.5±9.0 |
Morphine/6-MAMa | 52 | 89% | 11% | 33.2±8.7 |
Cannabis/marijuana (THC in blood)b | 7750 | 94% | 6% | 32.6±8.4 |
Cocaine and/or BZEc | 160 | 96% | 4% | 28.6±7.0 |
Ecstasy | 483 | 92% | 8% | 26.4±7.2 |
GHB | 548 | 96% | 4% | 26.0±6.8 |
Drug present in venous blood samples . | Number of cases . | Men (%) . | Women (%) . | Age of suspects (mean±SD) (years) . |
---|---|---|---|---|
Ethanol | 32 814 | 90% | 10% | 40.0±8.7 |
Amphetamine | 9162 | 85% | 15% | 36.5±9.0 |
Morphine/6-MAMa | 52 | 89% | 11% | 33.2±8.7 |
Cannabis/marijuana (THC in blood)b | 7750 | 94% | 6% | 32.6±8.4 |
Cocaine and/or BZEc | 160 | 96% | 4% | 28.6±7.0 |
Ecstasy | 483 | 92% | 8% | 26.4±7.2 |
GHB | 548 | 96% | 4% | 26.0±6.8 |
6-MAM=6-acetylmorphine, a metabolite of heroin.
THC=tetrahydrocannabinol, the active constituent of marijuana/cannabis.
BZE=benzoylecgonine, an inactive metabolite of cocaine.
The relationship between the concentration of a certain drug in blood and the degree of impairment of cognitive and psychomotor functioning varies widely, owing to the development of tolerance and other individual characteristics.67–70 Accordingly, impairment-based drugged driving laws were not very effective, because tangible evidence of impairment was not easy to obtain, even after clinical tests were made by physicians or police officers trained to recognize drug impairment. The legal framework behind concentration per se DUID laws is different, because the main evidence for a prosecution is essentially the toxicology result and concentration of a banned substance in the driver's blood and not the effects of the drug or impairment caused by a particular substance.71,72
Table 1.4 shows descriptive statistics for the concentrations of drugs determined in venous blood from people suspected of DUID in Sweden.
Mean, median and highest concentrations of the drugs most commonly identified in blood from people arrested for driving under the influence of drugs in Sweden.
Drug present in blood . | Number of cases . | Mean conc. (mg L−1) . | Median conc. (mg L−1) . | Highest conc. (mg L−1) . |
---|---|---|---|---|
Ethanol | 32 814 | 1740 | 1780 | 5180 |
Amphetamine | 9162 | 0.77 | 0.60 | 22.3 |
Methamphetamine | 644 | 0.34 | 0.20 | 3.7 |
Ecstasy (MDMA) | 493 | 0.23 | 0.10 | 3.5 |
Tetrahydrocannabinol (THC) | 7750 | 1.9 | 1.0 | 36 |
γ-Hydroxybutyrate (GHB) | 548 | 89 | 82 | 340 |
Cocaine | 160 | 0.069 | 0.05 | 0.31 |
Benzoylecgoninea | 160 | 0.80 | 0.60 | 3.0 |
Morphineb,c | 2029 | 0.046 | 0.03 | 1.13 |
6-MAMb | 52 | 0.016 | 0.01 | 0.10 |
Codeineb,c | 1391 | 0.047 | 0.01 | 2.4 |
Diazepamc | 1950 | 0.36 | 0.20 | 6.2 |
Drug present in blood . | Number of cases . | Mean conc. (mg L−1) . | Median conc. (mg L−1) . | Highest conc. (mg L−1) . |
---|---|---|---|---|
Ethanol | 32 814 | 1740 | 1780 | 5180 |
Amphetamine | 9162 | 0.77 | 0.60 | 22.3 |
Methamphetamine | 644 | 0.34 | 0.20 | 3.7 |
Ecstasy (MDMA) | 493 | 0.23 | 0.10 | 3.5 |
Tetrahydrocannabinol (THC) | 7750 | 1.9 | 1.0 | 36 |
γ-Hydroxybutyrate (GHB) | 548 | 89 | 82 | 340 |
Cocaine | 160 | 0.069 | 0.05 | 0.31 |
Benzoylecgoninea | 160 | 0.80 | 0.60 | 3.0 |
Morphineb,c | 2029 | 0.046 | 0.03 | 1.13 |
6-MAMb | 52 | 0.016 | 0.01 | 0.10 |
Codeineb,c | 1391 | 0.047 | 0.01 | 2.4 |
Diazepamc | 1950 | 0.36 | 0.20 | 6.2 |
6-MAM=6-acetylmorphine, a metabolite of heroin.
THC=tetrahydrocannabinol, the active constituent of marijuana/cannabis.
BZE=benzoylecgonine, an inactive metabolite of cocaine.
Although the statutory blood–alcohol limit for driving (since 1989) is 20 mg per 100 mL (0.02 g%), the median blood–alcohol concentration (BAC) in apprehended drivers is 170 mg per 100 mL, which is more than eight times above the legal limit.73 Reaching such a high BAC requires binge drinking and most of the traffic delinquents suffer from an alcohol abuse problem and clinically they might be diagnosed as alcoholics (also see Chapter 14).74 This makes it tempting to suggest that mandatory treatment and rehabilitation for substance abuse might be more worthwhile than conventional punishments for drunken driving, such as monetary fines, revocation of the driving permit or short terms of imprisonment.75,76
Likewise, the median concentration of amphetamine in the blood of drivers apprehended by the police in Sweden was 0.6 mg L−1, which verifies that large doses of this central stimulant were ingested some time before driving.77 Amphetamine has a few legitimate therapeutic uses, such as attention deficit disorder, but when used for this reason the peak concentrations in blood are rarely higher than 0.1–0.2 mg L−1.77 Among drivers killed in traffic crashes with amphetamine determined in blood at autopsy, the median concentrations was 1.0 mg L−1 and 75% of the deceased had been arrested previously for use of illicit drugs or DUID.78
1.6 Drug-facilitated Sexual Assault
Drug-related violent crimes, such as drug-facilitated sexual assault (DFSA), are common in most communities and the news media sometimes refer to this behavior as date-rape.79,80 When complaints of sexual assault are brought to the attention of the police authorities, the sampling of body fluids for toxicology should be done without delay. A typical case scenario might involve a perpetrator adding (spiking) a victim's food or drink with an incapacitating drug to cause drowsiness and inability to resist sexual advances, and in this drug-induced state a crime was committed.80,81
The retrieval of forensic evidence in DFSA cases is often hampered because some victims do not report a crime to the police or do not seek treatment for injuries until many hours, sometimes days, afterwards. This delay in reporting means that alcohol and/or other drugs in the body are eliminated by metabolism and excretion processes, so forensic toxicology evidence of drug exposure is often lacking or negative. In this connection, obtaining hair strands or nail clippings several weeks or months after an offence can furnish useful information about drug use when the alleged crime was committed.82
Table 1.5 shows the drugs identified and the concentrations in blood in two studies of alleged sexual assault of females in Sweden spanning a period of 8 years.83,84 Many of the drugs identified represent ordinary prescription medications that might have been used by the victim at the time when the offence occurred. The police investigation needs to document the victim's recreational drug habits and what medication, if any, was being taken and in what dosage at the time the crime was committed. The commonest drug detected in blood at elevated concentrations was ethanol (mean 124 mg per 100 mL) with a range from <20 mg per 100 mL (negligible) to >300 mg per 100 mL (incapacitating).
The top 10 drugs identified in the blood of female victims of sexual assault based on two epidemiological studies done in 2003–2007 and 2008–2010, representing 3260 cases.83,84
Drug . | Period . | N . | Age (mean±SD) (years) . | Mean conc. (mg L−1) . | Median conc. (mg L−1) . | Highest conc. (mg L−1) . |
---|---|---|---|---|---|---|
Ethanol | 2003–2007 | 882 | 25±9.9 | 1240 | 1190 | 3700 |
2008–2010 | 791 | 25±10.3 | 1230 | 1220 | 4300 | |
Cannabis (THC) | 2003–2007 | 100 | 25±9.3 | 0.0012 | 0.0006 | 0.006 |
2008–2010 | 85 | 25±8.3 | 0.0010 | 0.0007 | 0.006 | |
Diazepam | 2003–2007 | 88 | 32±12.7 | 0.35 | 0.20 | 2.7 |
2008–2010 | 86 | 33±12.1 | 0.24 | 0.10 | 1.0 | |
Paracetamol | 2003–2007 | 68 | 20±10.4 | 7.7 | 5.0 | 48 |
2008–2010 | 88 | 29±12.6 | 6.5 | 5.0 | 25 | |
Amphetamine | 2003–2007 | 86 | 29±11.1 | 0.22 | 0.10 | 1.8 |
2008–2010 | 55 | 30±11.2 | 0.35 | 0.24 | 1.7 | |
Alprazolam | 2003–2007 | 55 | 27±11.4 | 0.05 | 0.04 | 0.17 |
2008–2010 | 33 | 32±12.3 | 0.06 | 0.04 | 0.19 | |
Zopiclone | 2003–2007 | 35 | 31±10.9 | 0.05 | 0.03 | 0.13 |
2008–2010 | 33 | 34±14.3 | 0.10 | 0.05 | 0.40 | |
Citalopram | 2003–2007 | 30 | 32±10.0 | 0.09 | 0.08 | 0.30 |
2008–2010 | 26 | 28±10.7 | 0.11 | 0.10 | 0.30 | |
Fluoxetine | 2003–2007 | 22 | 29±11.8 | 0.25 | 0.20 | 0.50 |
2008–2010 | 18 | 23±6.7 | 0.28 | 0.20 | 0.70 | |
Codeine | 2003–2007 | 29 | 36±11.8 | 0.06 | 0.05 | 0.35 |
2008–2010 | 17 | 39±8.2 | 0.07 | 0.08 | 0.16 |
Drug . | Period . | N . | Age (mean±SD) (years) . | Mean conc. (mg L−1) . | Median conc. (mg L−1) . | Highest conc. (mg L−1) . |
---|---|---|---|---|---|---|
Ethanol | 2003–2007 | 882 | 25±9.9 | 1240 | 1190 | 3700 |
2008–2010 | 791 | 25±10.3 | 1230 | 1220 | 4300 | |
Cannabis (THC) | 2003–2007 | 100 | 25±9.3 | 0.0012 | 0.0006 | 0.006 |
2008–2010 | 85 | 25±8.3 | 0.0010 | 0.0007 | 0.006 | |
Diazepam | 2003–2007 | 88 | 32±12.7 | 0.35 | 0.20 | 2.7 |
2008–2010 | 86 | 33±12.1 | 0.24 | 0.10 | 1.0 | |
Paracetamol | 2003–2007 | 68 | 20±10.4 | 7.7 | 5.0 | 48 |
2008–2010 | 88 | 29±12.6 | 6.5 | 5.0 | 25 | |
Amphetamine | 2003–2007 | 86 | 29±11.1 | 0.22 | 0.10 | 1.8 |
2008–2010 | 55 | 30±11.2 | 0.35 | 0.24 | 1.7 | |
Alprazolam | 2003–2007 | 55 | 27±11.4 | 0.05 | 0.04 | 0.17 |
2008–2010 | 33 | 32±12.3 | 0.06 | 0.04 | 0.19 | |
Zopiclone | 2003–2007 | 35 | 31±10.9 | 0.05 | 0.03 | 0.13 |
2008–2010 | 33 | 34±14.3 | 0.10 | 0.05 | 0.40 | |
Citalopram | 2003–2007 | 30 | 32±10.0 | 0.09 | 0.08 | 0.30 |
2008–2010 | 26 | 28±10.7 | 0.11 | 0.10 | 0.30 | |
Fluoxetine | 2003–2007 | 22 | 29±11.8 | 0.25 | 0.20 | 0.50 |
2008–2010 | 18 | 23±6.7 | 0.28 | 0.20 | 0.70 | |
Codeine | 2003–2007 | 29 | 36±11.8 | 0.06 | 0.05 | 0.35 |
2008–2010 | 17 | 39±8.2 | 0.07 | 0.08 | 0.16 |
The forensic pharmacokinetics of ethanol has been extensively studied and is well documented in the literature (see Chapter 14).85 This sometimes justifies making a back-calculation of the victim's BAC from the time of sampling blood to the time the alleged crime was committed.86 Many studies have found that a good average elimination rate of ethanol from blood is 15 mg per 100 mL per h, with a range from 10 to 25 mg per 100 mL per h.87 However, making a back-calculation is not advisable if only a urine sample is available for analysis from the victim, because converting urine alcohol concentration (UAC) to BAC is a dubious practice.88 The UAC/BAC ratio is highly variable, depending on many factors including time of last emptying the bladder, before voiding urine for toxicological analysis.89
The most prominent illicit drugs identified in blood of sexual assault victims in Sweden were amphetamine and cannabis (tetrahydrocannabinol, THC), although neither of these psychoactive substances are known to cause drowsiness and incapacitation after acute recreational doses. Most of the drugs listed in Table 1.5 were prescription medication, especially benzodiazepines (diazepam and alprazolam), antidepressants (citalopram and fluoxetine) or pain killers (codeine and paracetamol), which confirms the results from many previous DFSA studies.90
Several potentially incapacitating drugs were identified in blood samples, however, including the fast acting hypnotic zopiclone,91 which therefore might have been added to the victim's food or drink with criminal intent. However, any police investigation needs to ascertain whether the victim had a prescription for this medication and might have been medicating with the drug at the time the crime was committed. Accordingly, obtaining a positive toxicology report does not prove a drug was used to incapacitate a victim.
1.7 Concluding Remarks
The creation of a nationwide forensic toxicology database, as described here for Sweden, has permitted a large number of pharmacoepidemiological projects and, over the years, scores of original publications have been published.15 TOXBASE contains reference concentrations for hundreds of drugs and metabolites, both licit and illicit, and these can be compared with future cases involving the same drugs with which the laboratory might be involved.92
Several compilations of therapeutic, toxic and lethal concentrations of drugs are available for scrutiny in the literature, although these should be used and interpreted cautiously. The methods of drug analysis differ between laboratories and analytical cut-off concentrations for reporting positive results are not necessarily the same. Whether a single intoxicating substance or multiple drugs were involved is not always clarified in these compilations. This makes a big difference when toxicity is assessed, owing to the potential for adverse drug–drug or drug–alcohol interactions.53 Moreover, a critical review shows that the concentrations listed for many drugs in these compilations are simply copied from one list to another without any explanations given.93 Older analytical methods from the 1960–1970s sometimes failed to distinguish a parent drug from its major metabolite, which would not be acceptable in today's forensic toxicology laboratory.
The validity and acceptance of analytical toxicology results are highly dependent on the accuracy, precision, specificity of the method and the condition of the sample received for analysis. The quality of post-mortem blood can vary widely in terms of water content and the proportion of red cells to serum, and the specimen sometimes contains clots. The participation of laboratories in external proficiency tests of toxicological drug analysis is a pre-requisite for accreditation and the results need to be well documented and made available for inspection if and when required.
Sudden and unexpected death in an otherwise healthy individual with nothing remarkable found at autopsy draws attention to a possible poisoning or drug intoxication death. Under these circumstances the toxicology report is highly relevant when cause and manner of death are determined, whether self-administration (suicide), administration by others (homicide), self-administration for special purposes (drug abuse, abortion) or accidental overdosing with medication. Such information can also be gleaned from a search of TOXBASE.94,95
As discussed earlier, pre-analytical (sampling) variations dominate over analytical variations, which underscores the need for using reliable and reproducible sampling procedures to enhance integrity of the specimen analyzed.96,97 A well-known post-mortem artifact is redistribution of drugs into the vascular system after death, thereby increasing concentrations in blood. Many drugs tend to concentrate in lipid compartments or tissue depots and diffuse into the bloodstream as the time after death increases. For some drugs, especially those with large distribution volumes, concentrations in autopsy blood might be appreciably higher than the concentration at the time of death.98 The best choice of blood for toxicology is from a femoral vein in the legs and not central or cardiac blood for which drug concentrations are usually higher.99 Indeed, the cardiac/femoral concentration ratio is often used as an indicator of post-mortem redistribution.100
Some drugs are notoriously unstable in autopsy blood, as exemplified by the nitrobenzodiazepines, such as clonazepam, flunitrazepam and nitrazepam.101 Evidence of taking these sedative hypnotics during life is best obtained by analysis and quantification of their 7-amino metabolites.102 Furthermore, the illicit drug cocaine is degraded in vitro to its main metabolites benzoylecgonine and ecgonine methyl ester. The hypnotic drug zopiclone is also unstable and is transformed into 2-amino-5-chloropyridine (ACP). The analytical methods used by forensic toxicologists should be able to identify the parent drugs and the main metabolites as evidence of ante-mortem ingestion or exposure.103,104
The concentrations of some abused drugs, such as ethanol and GHB, can increase in the body after death, depending on conditions of storage (e.g. temperature and use of fluoride preservative) and whether any decomposition of the corpse had commenced.105,106 This requires using a higher analytical cut-off concentrations to report positive results, such as 30 mg L−1 for GHB in blood and 20 mg per 100 mL for ethanol, otherwise people might be falsely accused of ante-mortem ingestion of these substances. Some countries (e.g. Norway, Sweden and Poland) enforce low statutory BAC limits for driving (20 mg per 100 mL). Reporting an autopsy BAC above this limit is often interpreted to mean that the driver had consumed alcohol before the crash and was above the legal limit. Such a conclusion would have serious consequences for next of kin when insurance claims are made. The routine analytical methods used in toxicology laboratories to determine BAC cannot distinguish ethanol derived from drinking alcoholic beverages during life from ethanol generated by bacteria and micro-organisms after death.106,107
Interpretation of ethanol concentrations in autopsy blood is made more reliable if alternative specimens are analyzed, such as urine, vitreous humor and blood from different sampling sites, such as heart, iliac, subclavian and femoral veins.106,108 Another approach to distinguish ante-mortem ingestion from post-mortem synthesis of ethanol is to identify the non-oxidative metabolites ethyl glucuronide or ethyl sulfate, along with ethanol.109,110 Because ethanol produced by fermentation is not conjugated with glucuronic acid, finding the presence of ethyl glucuronide in post-mortem blood supports ante-mortem ingestion of ethanol.111
The practice of comparing the concentrations of drugs determined in post-mortem blood with therapeutic concentrations in plasma or serum from living subjects is not recommended.57 Many drugs bind to plasma proteins and the concentrations in plasma or serum are higher than in erythrocytes and consequently also higher than in whole blood. Examples of serum/blood concentration ratios range from 1.15 : 1 for ethanol112 and 1.8 : 1 for diazepam46 to 2.0 : 1 for THC.113 Furthermore, post-mortem blood is highly variable in composition, which also impacts on the concentrations of drugs present.114
When results of the forensic autopsy and histopathology are inconclusive, attention shifts towards the possibility of drug intoxication as a cause of death. The information in TOXBASE becomes very important in such cases and functions as a reference material for drug concentrations.49 If the reference database of drug concentrations is sufficiently large, the information might be arranged according to age and gender of the deceased or the number of co-ingested drugs identified in blood samples.115,116 The TOXBASE available in Sweden classifies poisoning deaths as those involving a single intoxicating substance, a single drug together with an elevated blood–ethanol level or multiple drug deaths.9 As a reference material in the living, the post-mortem concentrations are compared with impaired drivers and, for many medicinal drugs, TDM cases can be used.115,116
TOXBASE was used to compile a list of drugs and drug concentrations determined in femoral blood representing all causes of death.35 These data provide a quick reference source to compare and contrast with future toxicology cases dealt with by the laboratory and analyzed by the same methods. The median and upper percentile points of the frequency distribution can be compared with the concentrations of the same drugs in new autopsy cases. For example, if a new case contained a concentration above the 97.5th percentile, then only 2.5% of all previous cases reached such a high concentration. This should raise a warning flag for the pathologist to consider, along with other information such as age and gender of the deceased and the types and concentrations of other drugs in the same blood sample.117
Whether evidence-based post-mortem toxicology will ever become a reality remains to be seen, although whatever happens TOXBASE will prove very useful for developing this project. Recommendations and general guidelines for good laboratory practice in forensic toxicology already exist in the UK and Ireland118 as well the USA, as published by the Society of Forensic Toxicologists (SOFT) organization (www.SOFT.org). More recently in the USA a Scientific Working Group for Forensic Toxicology (www.SWGTOX.org) was organized with the mission to develop and disseminate consensus standards for analytical methods suitable for toxicological analysis, including training and certification of analysts.
Both clinical and forensic toxicology laboratories have much to gain by creating a nationwide toxicology database.119,120 The treatment of poisoned patients, including the best available antidotes and their effectiveness, is other information that can be retrieved from clinical toxicology databases.121 Ethical questions often arise when large databases of information are available and searched on-line, and it is important to ensure that individual patients or police suspects are not identifiable by name.120
The Swedish TOXBASE was created in 1992 and contains enormous amounts of information about drugs and metabolites identified in blood samples from living and deceased persons. The material is homogeneous and the information is used for research and routine purposes when questions arise about the harmfulness of drugs and various drug combinations. Interpreting the meaning of drug concentrations in blood and the risk for drug-induced intoxication or toxicity are often contentious issues when expert testimony is presented to the court.122 The probability of encountering critical concentration of drugs in blood can be gleaned by a search of TOXBASE. The results can sometimes function as an early warning system to spot trends in drug abuse in society, such as the so-called “legal highs”, so that measures can be taken to classify them as controlled substances.