Collecting samples

Part of poison’s popularity is that it’s sneaky. Toxins rarely leave behind visible clues, so finding a toxin, and enough evidence to determine that it was the cause of death, is a tricky business that involves several specialized tests and a variety of bodily tissues and fluids.

The best places to obtain samples for testing are the locations where chemicals enter the body, where chemicals concentrate within the body, and along the routes of elimination. Thus blood, stomach contents, and tissues around injection sites may possess high concentrations of the drug. Analyses of liver, brain, and other tissues can reveal where a drug or its metabolites accumulated. Finally, urine testing can indicate where the drug and its metabolites are concentrated for final elimination. Check out these potential sources of illicit toxins:

• Blood: Blood by far is the toxicologist’s most useful substance. After all, the bloodstream is how toxins, whether injected or absorbed through the stomach or the lungs, are spread through the body. With modern toxicological techniques, you can find essentially any drug and its major metabolites in the blood. Blood examination tells the toxicologist what was going on in the body at the time of death. Concentrations of medicines and drugs within the blood correlate well with levels of intoxication and with levels that are potentially lethal.

• Urine: Easily sampled with a cup and a trip to the restroom, urine testing is a staple of workplace drug testing. It can also prove useful during an autopsy. Because kidneys are situated along one of the body’s major drug and toxin elimination routes, toxicologists can often find such substances in greater concentrations in the urine than in the blood. However, the correlation between urine concentration of a drug and its effects in the body is poor, at best. The urine level can reveal that the drug had been in the blood at some earlier time, but it can’t determine whether the drug was exerting any effect on the individual at the time it was collected.

  Likewise, toxicologists can’t estimate blood concentrations from urine concentrations. The concentration of any drug in the urine depends on how much urine the individual produced. If someone drank a great deal of water, the urine and any chemicals it contains become more diluted than they are for someone who hasn’t consumed large quantities of water.

• Stomach contents: Doctors remove the stomach contents of survivors of drug ingestions by way of a gastric tube, which typically passes through the nose and into the stomach. The contents then are lavaged, or washed, from the stomach and tested for the presence of drugs or poisons. During an autopsy, examiners test stomach contents in the same way. Obtaining stomach contents is critical in cases where investigators suspect poison or drug ingestion. However, the concentration of any drugs found in the stomach doesn’t correlate with their levels in the blood and thus their effects on the person.
• Liver: The liver is intimately involved in drug and toxin metabolism (destruction). Testing liver tissue and the bile it produces often reveals a drug or its metabolites. Many drugs, particularly opiates, tend to concentrate in the liver and the bile, so investigators can measure them in these tissues, even when blood tests show no traces of them. The liver may reflect levels of a drug during the hours before death, and the bile may indicate what drugs were in the system during the past three to four days.
• Vitreous humor: Vitreous humor is the liquid in the eyeball. It’s fairly resistant to putrefaction (decay), and in severely decomposed corpses, it may be the only remaining fluid. The vitreous humor is a water-like fluid, which means that water-soluble chemicals dissolve in it. Furthermore, vitreous humor and blood maintain equilibrium, meaning that any water-soluble chemical in the blood also is in the vitreous humor. But substance levels in the vitreous lag behind levels found in the blood by about one to two hours, so testing the vitreous reflects the concentration of the toxin in the blood one to two hours earlier.
• Hair: Hair absorbs certain heavy-metal toxins (arsenic, lead, and others) and has the unique ability of providing an intoxication timeline for many of these substances. I discuss this fact in greater detail in the “Interpreting the results” section later in the chapter.
• Insects: Toxicologists can even test insects that feed on corpses for drugs in cases of severely decomposed bodies. Because certain drugs tend to concentrate in the tissues of these bugs, they may supply information about whether a drug was present in the deceased.

Determining the cause and manner of death

The medical examiner ultimately is responsible for determining the cause and manner of death, and toxicological findings can play an important role in making those determinations. Unfortunately, toxicological findings rarely provide a black-and-white, clear-cut answer, because drugs and poisons may be the cause or merely a contributing factor in any cause or manner of death.

Presuming the results

Screening, or presumptive testing, comes in many varieties. Common toxicological screening tests include the following:

• Color tests are chemical tests in which a reagent (chemical solution) is added to the substance (usually blood, urine, or tissue) being tested. A color change occurs whenever the suspected chemical is present. The color change results from a chemical reaction between the drug and the reagent, which produces a new compound that imparts a specific color to the mixture. These tests are cheap, easy, and quick, and they determine whether a specific chemical or class of chemicals is present in the material being tested.
• Immunoassays involve an antigen-antibody reaction. The substance being sought is the antigen, and the testing reagent is the antibody. An antibody reacts only with antigens that it recognizes and ignores all others. In this test, the toxicologist adds an antibody that can specifically identify the suspected substance to the sample. For example, if blood is to be tested for amphetamines, the toxicologist adds an antibody specific to amphetamines to a sample of the blood. A reaction gives him a positive result.
• Thin-layer chromatography (TLC) is an inexpensive screening test that presumptively identifies hundreds of compounds at once by separating compounds according to how far they move through an absorbent material (usually a silica gel) when combined with a solvent. The compounds are then identified by comparing their respective movements with the movements of known standards. This test uses a color reaction that further identifies the compound. Check out Chapter 19 for more information on this test.
• Gas chromatography (GC) is a method of separating compounds according to their respective sizes, shapes, and chemical properties. GC can identify the class of an unknown or suspected chemical but can’t give its exact makeup. As with TLC, GC is useful as a screening tool, and more importantly, it separates the components of a chemical mixture for later confirmatory testing. Chapter 8 tells you more about gas chromatography.
• Ultraviolet (UV) spectroscopy takes advantage of the fact that different compounds absorb or reflect light in differing amounts and at varying wavelengths. When exposed to UV light, compounds or classes of compounds absorb UV light more strongly at specific wavelengths and less so at other wavelengths. The magnitude of the light absorption at the wavelength of maximum absorption indicates the concentration of the suspected drug or chemical in the sample.

Confirming the results

A good confirmatory test is sensitive and specific, recognizes the chemical in question, and can identify it to the exclusion of all others. After a chemical has undergone a screening test and the toxicologist has established a presumptive identity, a confirmatory test can accurately determine the true identity of the unknown substance.

The most important confirmatory test used by the toxicologist is mass spectrometry (MS). I discuss this process in detail in Chapter 8. When the toxicologist compares the mass spectrums of unknown and known substances, the identity of the unknown sample comes to light. In the forensic toxicology laboratory, MS usually is employed in combination with gas chromatography. This combination is called gas chromatography/mass spectrometry (GC/MS). In GC/MS, GC separates the test sample into components, and MS identifies each of those components.

Infrared spectroscopy also determines the chemical fingerprint of the substance being tested but exposes the substance to infrared light instead of electrons. When exposed to infrared light, each compound transmits, absorbs, and reflects the light in its own unique pattern. These unique patterns determine which compounds are present and thus identify the chemical substance being tested.

Interpreting the results

After testing has revealed the presence and concentration of a chemical substance, the hard part begins. The toxicologist now must assess what the results mean, evaluating each of the drugs present, identifying routes of administration, and determining whether concentrations that are present played a role in the subject’s behavior or death. From such determinations, the toxicologist decides whether a drug could have caused the victim to lose control of a car or exhibit violent or aggressive behavior, for example, and whether a drug caused or contributed to the victim’s death.

The route of entry of a toxin is extremely important. If a drug was injected into a person who had no means of injecting it or into a site that makes self-administration unlikely, homicide will be a stronger consideration.

In general, the concentration of the drug or poison is greatest at the site where it’s administered. For example:

• Ingested toxins show up in the stomach, intestines, or liver.
• Inhaled gases are concentrated in the lungs.
• Toxins that are injected intramuscularly linger in the tissues around the injection site. Drugs injected into muscle are slowly picked up by the blood and transported throughout the body.
• Drugs that are given intravenously (IV) bypass the stomach and liver, entering the bloodstream directly. Thus, they’re quickly distributed throughout the body, and none remain at the IV injection site. The toxicologist may find high concentrations of the drug in the blood and in multiple tissues of the body but little or none in the stomach and liver (as would be seen with ingestion).

Finding a large amount of a toxin in the victim’s stomach doesn’t necessarily mean that the drug was the cause of death; it may not yet have been absorbed into the blood and distributed to the body. Thus, the level of the drug in the blood is more important than the concentration of the drug in the stomach contents. The toxicologist must see evidence that the drug was absorbed before he can attribute harm or death to the drug.

After determining a blood level of a certain chemical, the toxicologist assigns the level one of these four broad categories:

• Normal: This level is the one that is expected in the general population under normal circumstances.
• Therapeutic: This is the level that your doctor wants you to reach when you’re taking a prescription medication. It’s the blood level of the drug that brings about the most beneficial effect.
• Toxic: A toxic level is one that may cause harm — nausea, vomiting, or a drastic change in the heart’s rhythm, for example — or death.
• Lethal: This is the level at which the drug in question consistently causes death. In toxicology, the term LD50 describes the measurement of a chemical’s lethal potential. The LD50 of a drug is the blood concentration at which 50 percent of the people taking it die from that intake.

You can see some wiggle room in each of these categories. Everyone reacts to chemicals and toxins differently. Much of this variance relates to age, sex, body size and weight, genetics, and nutritional and health status. A young, robust, and healthy individual usually tolerates more of a given drug than someone who is old, thin, and sickly. Drug addicts commonly ingest or inject doses of cocaine or heroin that would kill the uninitiated in minutes, and alcohol abusers can walk around with blood-alcohol levels that would flatten a nondrinker. Toxicologists must consider these factors when assessing whether a given level of a drug is toxic or lethal and whether it contributed to the subject’s behavior or death.

In general, the concentration of a drug or its metabolites in urine doesn’t reliably indicate the effects of the drug on the subject. The physiological effects of the drug depend upon its concentrations within the blood and various tissues of the body, including the brain. Many drugs and their metabolites are concentrated in the urine in preparation for elimination from the body, which means the concentration may be falsely high. A time lag exists between when the drug is at maximum concentration in the blood and thus has its maximum effect on the individual, and when it appears in and concentrates in the urine. Simply put, the elimination process takes time, so the urine concentration lags behind the blood concentration.

At times, toxicologists are called upon to determine whether a poisoning is acute (quick but intense) or chronic (drawn out in small doses). A good example is arsenic poisoning. Arsenic can kill when it’s given in a single large dose or when it’s given in repeated small doses during the course of weeks or months. In either case, the blood level may be high. But determining whether the poisoning was acute or chronic may be extremely important. The suspect list for an acute poisoning may be long, but the suspect list for a chronic poisoning would include only those who had long-term contact with the victim. A family member, a caretaker, or a family cook would qualify.

Toxicologists use the victim’s hair to determine whether a poisoning was acute or chronic. Hair analysis not only reveals exposure to arsenic but also provides a timeline of the exposure. Arsenic, for example, is deposited in the cells of the hair follicles in proportion to the blood level of the arsenic at the time the cell was produced. As hair grows, hair follicle cells undergo changes and are incorporated into the growing hair shaft. In general, hair grows about half an inch in length per month. So the toxicologist can cut the hair into short segments and then measure the arsenic levels of each, thus revealing a timeline of the victim’s exposure to arsenic. This evidence can be critical in assessing chronic or episodic poisonings.

Understanding alcohol

Ethanol, or drinking alcohol, is by far the most commonly abused drug. Its toxic effects are potentially lethal, and the loss of coordination and poor judgment associated with its use can lead to violent and negligent acts. Alcohol is physically addictive, and withdrawal can be an arduous and dangerous process. Without proper medical treatment for alcohol addiction, death rates from withdrawal syndromes such as delirium tremens (DTs) can be 20 percent or more.

Blood-alcohol concentration (BAC) correlates very well with the degree of intoxication. The level is expressed in grams percent, or the number of grams of alcohol in every 100 milliliters of blood. As the BAC level rises, the toxic effects of the alcohol become more pronounced. A level of 0.08 percent is the legal limit for intoxication in most jurisdictions. You may become impaired at a much lower level, but at 0.08 percent, they’ll cuff you.

At a level of 0.03 percent, which for most people is the equivalent of consuming a single beer or one highball, you become giddy, but your motor skills show few ill effects. Between 0.03 percent and 0.08 percent, coordination, reaction time, and judgment decline. At a BAC above 0.12 percent, nausea and vomiting can occur, and at 0.25 percent, you’re likely to go into a coma. Levels at or above 0.30 percent often lead to deep coma, and above 0.40 percent, death is likely.

A police officer who detains you as a suspect for driving under the influence (DUI) goes through several steps to determine whether you are, indeed, intoxicated. The first is a field sobriety test, in which the officer asks you to stand on one foot, stand steady with your eyes closed, repeatedly touch one finger to your nose, or walk a straight line in the heel-to-toe manner. These are done to determine how the alcohol you’ve consumed is affecting the coordination and balance centers of your brain. Alcohol makes performing each of these tasks clumsy or even impossible. Contrary to what many think, you can’t fake a field sobriety test. Physiology conspires against you, and you end up stumbling, wavering, or poking yourself in the eye.

The officer may also ask you to take a breath test (see the sidebar “Exhaling the evidence: Breathalyzer tests”). If so, you’re probably cooked. Alcohol passes unchanged through the lungs, going directly from the bloodstream into the air sacs of the lungs and out with each breath, so you can’t fake a breath test, either. The alcohol content in your lungs directly correlates with your blood-alcohol level. The higher the level in your blood, the higher the concentration in your exhaled breath. A breath test, therefore, is extremely accurate.

If you fail a field sobriety test or a breath test, a blood-alcohol concentration (BAC) test may be performed to determine the exact level, particularly if you’ve been involved in an accident or caused property damage, bodily harm, or the death of another. Most hospitals and crime labs can accurately and rapidly determine your BACs. The preferred testing method is gas chromatography (see the earlier section “Presuming the results”).

In suspected alcohol-caused deaths, the ME measures the alcohol level in cadaver blood to determine whether the intoxication level is high enough to have caused or contributed to the death. However, the blood-alcohol level in some corpses actually increases because of the action of bacteria, some of which produce alcohol. To get around this problem, the ME makes a determination of the alcohol level in the vitreous humor of the eye because it reflects a blood-alcohol level with a one- to two-hour lag. So, the vitreous humor can tell the ME what the blood-alcohol level was one to two hours before death.

Embalming a body may make determining the blood-alcohol level at the time of death difficult, if not impossible. During the embalming process, embalming fluid replaces most of the blood, leaving behind little for testing, in most cases. The embalming fluid also contains alcohol, but it’s methanol and not ethanol (drinking alcohol). Because the alcohol in the embalming material doesn’t enter the vitreous humor after death, the toxicologist can test the vitreous for ethanol. If ethanol turns up in the vitreous humor, it had to have been in the victim’s blood before death.

Getting down with depressants

Opiates, barbiturates, alcohol, and other tranquilizers are central nervous system (CNS) depressants that make you sleepy and lethargic and thus are referred to as downers.

Hopping up: Stimulants

The most commonly used stimulants, or uppers, are amphetamines and cocaine. They increase alertness, lessen fatigue, and suppress appetite. However, with continued use, they also cause irritability, anxiousness, aggressive behavior, paranoia, fatigue, and depression. These reactions make sense because people who are hopped up all the time tend to eat and sleep poorly, overreact to stress, and simply vibrate through life, which is likely to wear anyone out. Furthermore, when it does, physical fatigue and mental exhaustion set in, which may be why one slang name for certain amphetamines is crank — they make the user unpleasant and cranky.

Users of stimulants often develop tachyphylaxis, which means that the body gets used to them, thus lessening their effects. As a result, people who abuse stimulants must take ever-increasing amounts to get the same kick. One cause of tachyphylaxis is that the body produces more of the enzymes that metabolize these drugs, so they’re destroyed and eliminated at faster rates.

Amphetamines, such as crystal methamphetamine, are highly addictive, widely abused, and easily manufactured in garage labs. Because abuse of these compounds is common and widespread, testing for amphetamines is part of virtually every hospital and crime lab toxicology screen.

In the bloodstream, cocaine is converted to methylecgonine and benzoylecgonine. Urine tests target the latter of these two compounds and can find traces for up to three days after the last use. Toxicologists use both immunoassay and the Scott Color Test as screening tests for cocaine.

Taking a trip with hallucinogens

Hallucinogens are trippy. They alter perceptions and mood, lead to delusional thinking, and cause hallucinations. Delusions basically are false beliefs that have little or no basis in reality. Hallucinations are sensory experiences that aren’t real and can affect any or all of the senses; they can be visual (sight), auditory (sound), olfactory (smell), taste, or tactile (touch).

The most frequently encountered hallucinogens come either from the plant world (marijuana, peyote, and mushrooms) or the chemistry laboratory (LSD, STP, and PCP).

Dirty deeds: Date rape drugs

You’ve no doubt heard of the so-called date-rape drugs or rave drugs. They’ve been the subject of a considerable number of criminal actions and civil litigations. The conviction of Andrew Luster, the heir-apparent to the Max Factor fortune, was based on his illicit use of GHB (gamma-hydroxybutyrate).

The major date-rape drugs are Rohypnol (flunitrazepam), Ecstasy (3,4-methylenedioxymethamphetamine), GHB, and ketamine (ketamine hydrochloride).

These drugs cause sedation, a degree of compliance, poor judgment, and amnesia of events that occur while under their influence. The loss of event memory makes these drugs effective in date-rape situations. A criminal can easily slip a small amount of GHB or Rohypnol into the victim’s drink or a bottle of seemingly innocuous water. The victim may then leave with the would-be assailant because the drug impairs judgment and enhances euphoria. Only later does the victim realize that something happened, but memories of events are spotty or even absent altogether.

Recreational use of any of these drugs is a proverbial crapshoot. The quality and purity are variable, even with the pharmaceutically manufactured Rohypnol and ketamine, because they often are cut (combined with other materials, such as talc) or mixed with other drugs by the time they reach the street. Thus, users know neither what drugs nor exactly what amounts they’re ingesting. And because reactions vary widely from person to person and are unpredictable, you need to make a huge leap of faith to start using these dangerous chemicals — even more frightening when you realize that many people actually use any number of different drugs at the same time. Unfortunately, many young people willingly experiment with them and end up visiting the morgue.

Ecstasy is an amphetamine and appears in most routine drug screens, but the other drugs in this category aren’t typically part of such screening. However, they can be easily detected using the combination of gas chromatography and mass spectroscopy (GC/MS — see the earlier section “Confirming the results”).

Sniffing and huffing

An odd, but not rare, form of substance abuse is the sniffing of volatile chemicals. This practice also is known as huffing. It began with glue and gasoline but has spread to include napthalene (moth balls), toluene (paint thinners, fingernail polish, and some paints), and trichloroethylene (paint thinners and liquid typewriter correction fluid). Other commonly abused gases are gasoline, kerosene, and nitrous oxide (the “laughing gas” used by dentists).

People who inhale the fumes of these volatile chemicals can experience giddiness, euphoria, dizziness, slurred speech, headache, nausea, and vomiting. With continued exposure, loss of consciousness, coma, and death can follow. Permanent damage to the brain, liver, heart, and kidneys also can occur.

Because these gases are volatile, they rapidly break down in the body or are quickly excreted through the lungs. The toxicologist therefore may not be able to find them in the blood or tissues of the user. Often, the toxicologist determines the chronic use of these dangerous chemicals by finding damage to the liver, lungs, and kidneys of the user.

Bulking up

The abuse of anabolic steroids has become epidemic among athletes. These hormones appear naturally in the body in very small amounts, and when taken in large amounts, they cause muscle growth, increased strength, and improved reflexes — exactly what an athlete needs to compete. But steroids are a double-edged sword. They also cause hair loss, impotence, and liver damage (including liver cancer), and can lead to aggressive behavior (called “steroid rage”).

Users typically are easy to recognize as they tend to be big, muscular, and athletic. The screening and confirmatory tests mentioned earlier in this chapter detect most synthetic steroid preparations, but unscrupulous chemists constantly create newer and more difficult to detect “designer” steroids. The forensic toxicologist must continually search for new testing techniques to find these banned drugs in athletes.