Three job tasks of a forensic toxicologist

Review Of Forensic Science:

After studying this chapter you should be able to: Explain how alcohol is absorbed into the bloodstream, transported throughout the body, and eliminated by oxidation and excretion

Understand the process by which alcohol is excreted in the breath via the lungs

Understand the concepts of infrared and fuel cell breath-testing devices for alcohol testing

Describe commonly employed field sobriety tests to assess alcohol impairment

List and contrast laboratory procedures for measuring the concentration of alcohol in the blood

Relate the precautions to be taken to properly preserve blood in order to analyze its alcohol content

Understand the significance of implied-consent laws and the Schmerber v. California and Missouri v. McNeely cases to traf- fic enforcement

Describe techniques that forensic toxicologists use to isolate and identify drugs and poisons

Appreciate the significance of finding a drug in human tissues and organs to assessing impairment

Understand the drug recognition expert program and how to coordinate it with a forensic toxicology result

forensic toxicology

absorption acid alveoli anticoagulant artery base capillary excretion fuel cell detector metabolism oxidation pH scale preservative toxicologist vein

KEY TERMS

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300 CHAPTER 12

It is no secret that in spite of the concerted efforts of law enforcement agencies to prevent distri- bution and sale of illicit drugs, thousands die every year from intentional or unintentional admin- istration of drugs, and many more innocent lives are lost as a result of the erratic and frequently uncontrollable behavior of individuals under the influence of drugs. But one should not automati- cally attribute these occurrences to the wide proliferation of illicit-drug markets. For example, in the United States alone, drug manufacturers produce enough sedatives and antidepressants each year to provide every man, woman, and child with about 40 pills. All of the statistical and medi- cal evidence shows ethyl alcohol, a legal over-the-counter drug, to be the most heavily abused drug in Western countries.

Role of Forensic Toxicology Because the uncontrolled use of drugs has become a worldwide problem affecting all segments of society, the role of the toxicologist has taken on new and added significance. Toxicologists detect and identify drugs and poisons in body fluids, tissues, and organs. Their services are required not only in such legal institutions as crime laboratories and medical examiners’ offices; they also reach into hospital laboratories—where the possibility of identifying a drug overdose may represent the difference between life and death—and into various health facilities responsible for monitoring the intake of drugs and other toxic substances. Primary examples include perform- ing blood tests on children exposed to leaded paints or analyzing the urine of addicts enrolled in methadone maintenance programs.

The role of the forensic toxicologist is limited to matters that pertain to violations of crimi- nal law. However, the responsibility for performing toxicological services in a criminal justice system varies considerably throughout the United States. In systems with a crime laboratory independent of the medical examiner, this responsibility may reside with one or the other or may be shared by both. Some systems, however, take advantage of the expertise residing in gov- ernmental health department laboratories and assign this role to them. Nevertheless, whatever facility handles this work, its caseload will reflect the prevailing popularity of the drugs that are abused in the community. In most cases, this means that the forensic toxicologist handles numer- ous requests relating to the determination of the presence of alcohol in the body.

All of the statistical and medical evidence shows that ethyl alcohol—a legal, over-the-counter substance—is the most heavily abused drug in Western countries. Forty percent of all traffic deaths in the United States, nearly 17,500 fatalities per year, are alcohol related, along with more than 2 million injuries each year requiring hospital treatment. This highway death toll, as well as the untold damage to life, limb, and property, shows the dangerous consequences of alcohol abuse. Because of the prevalence of alcohol in the toxicologist’s work, we will begin by taking a closer look at how the body processes and responds to alcohol.

Toxicology of Alcohol The subject of alcohol analysis immediately confronts us with the primary objective of forensic toxicology: to detect and isolate drugs in the body so that their influence on human behavior can be determined. Knowing how the body metabolizes alcohol provides the key to understanding its effects on human behavior. This knowledge has also made possible the development of instru- ments that measure the presence and concentration of alcohol in individuals suspected of driving while under its influence.

Metabolism of Alcohol All chemicals that enter the body are eventually broken down by chemicals within the body and transformed into other chemicals that are easier to eliminate. This process of transformation, called metabolism, consists of three basic steps: absorption, distribution, and elimination.

ABSORPTION AND DISTRIBUTION Alcohol, or ethyl alcohol, is a colorless liquid normally diluted with water and consumed as a beverage. Alcohol appears in the blood within minutes after it has been consumed and slowly increases in concentration while it is being absorbed

metabolism The transformation of a chemical in the body to another chemical to facilitate its elimination from the body.

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from the stomach and the small intestine into the bloodstream. During the absorption phase, alcohol slowly enters the body’s bloodstream and is carried to all parts of the body. When the absorption period is completed, the alcohol becomes distributed uniformly throughout the watery portions of the body—that is, throughout about two-thirds of the body volume. Fat, bones, and hair are low in water content and therefore contain little alcohol, whereas alcohol concentration in the rest of the body is fairly uniform. After absorption is completed, a maximum alcohol level is reached in the blood, and the postabsorption period begins. Then the alcohol concentration slowly decreases until it reaches zero again.

Many factors determine the rate at which alcohol is absorbed into the bloodstream, includ- ing the total time taken to consume the drink, the alcohol content of the beverage, the amount consumed, and the quantity and type of food present in the stomach at the time of drinking. With so many variables, it is difficult to predict just how long the absorption process will require. For example, beer is absorbed more slowly than an equivalent concentration of alcohol in water, apparently because of the carbohydrates in beer. Also, alcohol consumed on an empty stomach is absorbed faster than an equivalent amount of alcohol taken when there is food in the stomach (see Figure 12–1).

The longer the total time required for complete absorption to occur, the lower the peak alcohol concentration in the blood. Depending on a combination of factors, maximum blood-alcohol concentration may not be reached until two or three hours have elapsed from the time of consumption. However, under normal social drinking conditions, it takes any- where from 30 to 90 minutes from the time of the final drink until the absorption process is completed.

ELIMINATION As the alcohol is circulated by the bloodstream, the body begins to eliminate it. Alcohol is eliminated through two mechanisms: oxidation and excretion. Nearly all of the alcohol consumed (95 to 98 percent) is eventually oxidized to carbon dioxide and water. Oxidation takes place almost entirely in the liver. There, in the presence of the enzyme alcohol dehydrogenase, the alcohol is converted into acetaldehyde and then to acetic acid. The acetic acid is subsequently oxidized in practically all parts of the body, becoming carbon dioxide and water.

The remaining alcohol is excreted, unchanged, in the breath, urine, and perspiration. Most significant, the amount of alcohol exhaled in the breath is in direct proportion to the concentra- tion of alcohol in the blood. This observation has had a tremendous impact on the technology and

absorption Passage of alcohol across the wall of the stomach and small intestine into the bloodstream.

oxidation The combination of oxygen with other substances to produce new products.

excretion Elimination of alcohol from the body in an unchanged state; alcohol is normally excreted in breath and urine.

FIGURE 12–1 Blood-alcohol concentrations after ingestion of 2 ounces of pure alcohol mixed in 8 ounces of water (equivalent to about 5 ounces of 80-proof vodka). Source: Courtesy U.S. Department of Transportation, Washington, D.C.

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Pulmonary artery

Vein

Body tissues

Artery

Lungs

RA LA

RV LV

Pulmonary vein

Simplified diagram of the human circulatory system. Dark vessels contain oxygenated blood; light vessels contain deoxygenated blood.

Alcohol in the Circulatory System

The extent to which an individual may be under the influence of alcohol is usually determined by mea- suring the quantity of alcohol present in the blood system. Normally, this is accomplished in one of two ways: (1) by direct chemical analysis of the blood for its alcohol content or (2) by measurement of the al- cohol content of the breath. In either case, the sig- nificance and meaning of the results can better be understood when the movement of alcohol through the circulatory system is studied.

Humans, like all vertebrates, have a closed circu- latory system, which consists basically of a heart and numerous arteries, capillaries, and veins. An artery is a blood vessel carrying blood away from the heart, and a vein is a vessel carrying blood back toward the heart. Capillaries are tiny blood vessels that interconnect the arteries with the veins. The exchange of materials between the blood and the other tissues takes place across the thin walls of the capillaries. A schematic dia- gram of the circulatory system is shown in the figure.

Ingestion and Absorption Let us now trace the movement of alcohol through the human circulatory system. After alcohol is ingested, it

inside the science moves down the esophagus into the stomach. About 20 percent of the alcohol is absorbed through the stom- ach walls into the portal vein of the blood system. The remaining alcohol passes into the blood through the walls of the small intestine. Once in the blood, the alco- hol is carried to the liver, where its destruction starts as the blood (carrying the alcohol) moves up to the heart.

The blood enters the upper right chamber of the heart, called the right atrium (or auricle), and is forced into the lower right chamber of the heart, known as the right ventricle. Having returned to the heart from its circulation through the tissues, the blood at this time contains very little oxygen and much carbon di- oxide. Consequently, the blood must be pumped up to the lungs, through the pulmonary artery, to be re- plenished with oxygen.

Aeration The respiratory system bridges with the circulatory sys- tem in the lungs, so that oxygen can enter the blood and carbon dioxide can leave it. As shown in the fig- ure, the pulmonary artery branches into capillaries ly- ing close to tiny pear-shaped sacs called alveoli. The lungs contain about 250 million alveoli, all located at the ends of the bronchial tubes. The bronchial tubes connect to the windpipe (trachea), which leads up to the mouth and nose (see the figure). At the surface of the alveolar sacs, blood flowing through the capillar- ies comes in contact with fresh oxygenated air in the sacs. A rapid exchange now proceeds to take place between the fresh air in the sacs and the spent air in the blood. Oxygen passes through the walls of the alveoli into the blood while carbon dioxide is dis- charged from the blood into the air (see the figure). If, during this exchange, alcohol or any other volatile substance is in the blood, it too will pass into the al- veoli. During breathing, the carbon dioxide and al- cohol are expelled through the nose and mouth, and the alveoli sacs are replenished with fresh oxygenated air breathed into the lungs, allowing the process to begin all over again.

The distribution of alcohol between the blood and alveolar air is similar to the example of a gas dis- solved in an enclosed beaker of water, as described on page 280. Here again, one can use Henry’s law to explain how the alcohol divides itself between the air and blood. Henry’s law may now be restated as follows: When a volatile chemical (alcohol) is dis- solved in a liquid (blood) and is brought to equi- librium with air (alveolar breath), there is a fixed ratio between the concentration of the volatile compound (alcohol) in air (alveolar breath) and its concentration in the liquid (blood), and this ratio is constant for a given temperature.

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tiny veins that fuse to form larger veins. These veins eventually lead back to the heart to complete the circuit.

During absorption, the concentra- tion of alcohol in the arterial blood is considerably higher than the concentra- tion of alcohol in the venous blood. One typical study revealed a subject’s arte- rial blood-alcohol level to be 41 percent higher than the venous level 30 minutes after the last drink.1 This difference is thought to exist because of the rapid diffusion of alcohol into the body tis- sues from venous blood during the early phases of absorption. Because the administration of a blood test requires drawing venous blood from the arm, this test is clearly to the advantage of a sub- ject who may still be in the absorption stage. However, once absorption is com- plete, the alcohol becomes equally dis- tributed throughout the blood system.

The temperature at which the breath leaves the mouth is normally 34°C. At this temperature, experimental evidence has shown that the ra- tio of alcohol in the blood to alcohol in alveoli air is approximately 2,100 to 1. In other words, 1 milliliter of blood will contain nearly the same amount of alcohol as 2,100 milliliters of alveo- lar breath. Henry’s law thus becomes a basis for relating breath to blood-alcohol concentration.

Recirculation and Distribution Now let’s return to the circulating blood. After emerging from the lungs, the oxygenated blood is rushed back to the upper left chamber of the heart (left atrium) by the pulmonary vein. When the left atrium contracts, it forces the blood through a valve into the left ventricle, which is the lower left cham- ber of the heart. The left ventricle then pumps the freshly oxygenated blood into the arteries, which carry the blood to all parts of the body. Each of these arteries, in turn, branches into smaller arter- ies, which eventually connect with the numerous tiny capillaries embedded in the tissues. Here the alcohol moves out of the blood and into the tis- sues. The blood then runs from the capillaries into

Pulmonary artery

Pulmonary vein

Bronchial tube

Carbon dioxide Alveolar sac

Carbon dioxide

Oxygen Alveolar sac

Oxygen

Gas exchange in the lungs. Blood flows from the pulmonary artery into vessels that lie close to the walls of the alveoli sacs. Here the blood gives up its carbon dioxide and absorbs oxygen. The oxygenated blood leaves the lungs via the pulmonary vein and returns to the heart.

Nasal cavity

Larynx

Trachea Esophagus

Bronchial tube

Alveolar sac

The respiratory system. The trachea connects the nose and mouth to the bronchial tubes. The bronchial tubes divide into numerous branches that terminate in the alveoli sacs in the lungs.

1 R. B. Forney et al., “Alcohol Distribution in the Vascular System: Concen- trations of Orally Administered Alcohol in Blood from Various Points in the Vascular System and in Rebreathed Air during Absorption,” Quarterly Journal of Studies on Alcohol 25 (1964): 205.

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artery A blood vessel that carries blood away from the heart.

vein A blood vessel that transports blood toward the heart.

capillary A tiny blood vessel across whose walls exchange of materials be- tween the blood and the tissues takes place; it receives blood from arteries and carries it to veins.

alveoli Small sacs in the lungs through whose walls air and other vapors are exchanged between the breath and the blood.

procedures used for blood-alcohol testing. The development of instruments to reliably measure breath for its alcohol content has made possible the testing of millions of people in a quick, safe, and convenient manner.

The fate of alcohol in the body is therefore relatively simple—namely, absorption into the bloodstream, distribution throughout the body’s water, and finally, elimination by oxida- tion and excretion. The elimination, or “burn-off,” rate of alcohol varies in different individ- uals; 0.015 percent w/v (weight per volume) per hour is the average rate after the absorption process is complete.2 However, this figure is an average that varies by as much as 30 percent among individuals.

BLOOD-ALCOHOL CONCENTRATION Logically, the most obvious measure of intoxication would be the amount of liquor a person has consumed. Unfortunately, most arrests are made after the fact, when such information is not available to legal authorities; furthermore, even if these data could be collected, numerous related factors, such as body weight and the rate of alcohol’s absorption into the body, are so variable that it would be impossible to prescribe uniform standards that would yield reliable alcohol intoxication levels for all individuals.

Theoretically, for a true determination of the quantity of alcohol impairing an individual’s normal body functions, it would be best to remove a portion of brain tissue and analyze it for alcohol content. For obvious reasons, this cannot be done on living subjects. Consequently, toxicologists concentrate on the blood, which provides the medium for circulating alcohol throughout the body, carrying it to all tissues including the brain. Fortunately, experimental evidence supports this approach and shows blood-alcohol concentration to be directly pro- portional to the concentration of alcohol in the brain. From the medicolegal point of view, blood-alcohol levels have become the accepted standard for relating alcohol intake to its effect on the body.

As noted earlier, alcohol becomes concentrated evenly throughout the watery portions of the body. This knowledge can be useful for the toxicologist analyzing a body for the presence of al- cohol. If blood is not available, as in some postmortem situations, a medical examiner can select a water-rich organ or fluid—for example, the brain, cerebrospinal fluid, or vitreous humor—to estimate the body’s equivalent alcohol level.

Testing for Intoxication From a practical point of view, drawing blood from veins of motorists suspected of being under the influence of alcohol is simply not convenient. The need to transport each suspect to a loca- tion where a medically qualified person can draw blood would be costly and time consuming, considering the hundreds of suspects that the average police department must test every year. The methods used must be designed to test hundreds of thousands of motorists annually, without causing them undue physical harm or unreasonable inconvenience, and provide a reliable diagno- sis that can be supported and defended within the framework of the legal system. This means that toxicologists have had to devise rapid and specific procedures for measuring a driver’s degree of alcohol intoxication that can be easily administered in the field.

Breath Testing for Alcohol The most widespread method for rapidly determining alcohol intoxication is breath testing. A breath tester is simply a device for collecting and measuring the alcohol content of alveolar breath. Alcohol is expelled, unchanged, in the breath of a person who has been drinking. A breath test measures the alcohol concentration in the pulmonary artery by measuring its concentration in alveolar breath. Thus, breath analysis provides an easily obtainable specimen along with a rapid and accurate result.

2 In the United States, laws that define blood-alcohol levels almost exclusively use the unit percent weight per volume—% w/v. Hence, 0.015 percent w/v is equivalent to 0.015 gram of alcohol per 100 milliliters of blood, or 15 milligrams of alcohol per 100 milliliters.

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Breath-test results obtained during the absorption phase may be higher than results obtained from a simultaneous analysis of venous blood. However, the former are more reflective of the concentration of alcohol reaching the brain and therefore more accurately reflect the effects of alcohol on the subject. Again, once absorption is complete, the difference between a blood test and a breath test should be minimal.

BREATH-TEST INSTRUMENTS The first widely used instrument for measuring the alcohol content of alveolar breath was the Breathalyzer, developed in 1954 by R. F. Borkenstein, who was a captain in the Indiana State Police. Starting in the 1970s, the Breathalyzer was phased out and replaced by other instruments. Like the Breathalyzer, they assume that the ratio of alcohol in the blood to alcohol in alveolar breath is 2,100 to 1 at a mouth temperature of 34°C. In other words, 1 milliliter of blood contains nearly the same amount of alcohol as 2,100 milliliters of alveolar breath. Unlike the Breathalyzer, modern breath testers are free of chemicals. These devices include infrared light–absorption devices and fuel cell detectors (described in the following “Inside the Science” box).

Infrared and fuel-cell-based breath testers are microprocessor controlled, so all an operator has to do is to press a start button; the instrument automatically moves through a sequence of steps and produces a readout of the subject’s test results. These instru- ments also perform self-diagnostic tests to ascertain whether they are in proper operating condition.

CONSIDERATIONS IN BREATH TESTING An important feature of these instruments is that they can be connected to an external alcohol standard or simulator in the form of either a liquid or a gas. The liquid simulator contains a known concentration of alcohol in water. It is heated to a controlled temperature and the vapor formed above the liquid is pumped into the instrument. Dry-gas standards typically consist of a known concentration of alcohol mixed with an inert gas and compressed in cylinders. The external standard is automatically sampled by the breath-test instrument before and/or after the subject’s breath sample is taken and recorded. Thus the operator can check the accuracy of the instrument against the known alcohol standard.

The key to the accuracy of a breath-testing device is to ensure that the unit captures the alcohol in the alveolar (i.e., deep-lung) breath of the subject. This is typically accomplished by programming the unit to accept no less than 1.1 to 1.5 liters of breath from the subject. Also, the subject must blow for a minimum time (such as 6 seconds) with a minimum breath flow rate (such as 3 liters per minute).

The breath-test instruments just described feature a slope detector, which ensures that the breath sample is alveolar, or deep-lung, breath. As the subject blows into the instrument, the breath-alcohol concentration is continuously monitored. The instrument accepts a breath sample only when consecutive measurements fall within a predetermined rate of change. This approach ensures that the sample measurement is deep-lung breath and closely relates to the true blood- alcohol concentration of the subject being tested.

A breath-test operator must take other steps to ensure that the breath-test result truly reflects the actual blood-alcohol concentration within the subject. A major consideration is to avoid mea- suring “mouth alcohol” resulting from regurgitation, belching, or recent intake of an alcoholic beverage. Also, recent gargling with an alcohol-containing mouthwash can lead to the presence of mouth alcohol. As a result, the alcohol concentration detected in the exhaled breath is higher than the concentration in the alveolar breath. To avoid this possibility, the operator must not al- low the subject to take any foreign material into his or her mouth for at least fifteen minutes be- fore the breath test. Likewise, the subject should be observed not to have belched or regurgitated during this period. Mouth alcohol has been shown to dissipate after fifteen to twenty minutes from its inception.

Measurement of independent breath samples taken within a few minutes of each other is another extremely important check of the integrity of the breath test. Acceptable agree- ment between the two tests taken minutes apart significantly reduces the possibility of er- rors caused by the operator, mouth alcohol, instrument component failures, and spurious electric signals.

fuel cell detector A detector in which chemical reac- tions produce electricity.

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306 CHAPTER 12

Infrared Light Absorption

In principle, infrared instruments operate no dif- ferently than the spectrophotometers described in Chapter 11. An evidential testing instrument that incorporates the principle of infrared light ab- sorption is shown in Figure 1. Any alcohol present in the subject’s breath flows into the instrument’s breath chamber. As shown in Figure 2, a beam of infrared light is aimed through the chamber. A fil- ter is used to select a wavelength of infrared light at which alcohol will absorb. As the infrared light passes through the chamber, it interacts with the alcohol and causes the light to decrease in inten- sity. The decrease in light intensity is measured by a photoelectric detector that gives a signal proportional to the concentration of alcohol pres- ent in the breath sample. This information is pro- cessed by an electronic microprocessor, and the percent blood-alcohol concentration is displayed on a digital readout. Also, the blood-alcohol level is printed on a card to produce a permanent rec- ord of the test result. Most infrared breath testers aim a second infrared beam into the same cham- ber to check for acetone or other chemical inter- ferences on the breath. If the instrument detects differences in the relative response of the two infrared beams that does not conform to ethyl alcohol, the operator is immediately informed of the presence of an “interferant.”

inside the science

DetectorInfrared radiation source

Sample chamber Filter

Breath inlet

Breath outlet

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Sample chamber

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Infrared light beamed through chamber. Alcohol in breath absorbs some infrared light.

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(a) An infrared breath-testing instrument—the Data Master DMT. (b) A subject blowing into the DMT breath tester.

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Field Sobriety Testing A police officer who suspects that an individual is under the influence of alcohol usually conducts a series of preliminary tests before ordering the suspect to submit to an evidential breath or blood test. These preliminary, or field sobriety, tests are normally performed to ascertain the degree of the suspect’s physical impairment and whether an evidential test is justified.

Field sobriety tests usually consist of a series of psychophysical tests and a preliminary breath test (if such devices are authorized and available for use). A portable handheld roadside breath tester is shown in Figure 12–2. This pocket-sized device weighs 5 ounces and uses a fuel cell to measure the alcohol content of a breath sample. The fuel cell absorbs the alcohol from the breath sample, oxidizes it, and produces an electrical current proportional to the breath-alcohol content. This instrument Figure 12–2 can typically perform for years before the fuel cell needs to be replaced. Its been approved for use as an evidential breath tester by the National Highway Traffic Safety Administration.

Horizontal-gaze nystagmus, walk and turn, and the one-leg stand constitute a series of reliable and effective psychophysical tests. Horizontal-gaze nystagmus is an involuntary jerking of the eye as it moves to the side. A person experiencing nystagmus is usually unaware

Infrared radiation source

Sample chamber Filter selects wavelength of IR light at which alcohol absorbs

Breath inlet

Breath outlet

Detector

Infrared radiation source

Sample chamber

Breath inlet

Breath outlet

Detector converts infrared light to an electrical signal proportional to the alcohol content in breath.

Infrared radiation source

Sample chamber

Breath inlet

Breath outlet

Detector Breath-alcohol content is converted into a blood-alcohol concentration and displayed on a digital readout.

Schematic diagram of an infrared breath-testing instrument.

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FIGURE 12–2 (a) The Alco-Sensor FST. (b) A subject blowing into the roadside tester device.

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The Fuel Cell

A fuel cell converts energy arising from a chemical re- action into electrochemical energy. A typical fuel cell consists of two platinum electrodes separated by an acid- or base-containing porous membrane. A plati- num wire connects the electrodes and allows a current to flow between them. In the alcohol fuel cell, one of the electrodes is positioned to come into contact with a subject’s breath sample. If alcohol is present in the breath, a reaction at the electrode’s surface converts the alcohol to acetic acid. One by-product of this con- version is free electrons, which flow through the con- necting wire to the opposite electrode, where they interact with atmospheric oxygen to form water (see the figure). The fuel cell also requires the migration of hydrogen ions across the acidic porous membrane to complete the circuit. The strength of the current flow between the two electrodes is proportional to the concentration of alcohol in the breath.

inside the science

Breath

Acetic acid

Oxygen

Alcohol H2O Outlet

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– e– e – e

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A fuel cell detector in which chemical reactions are used to produce electricity.

that the jerking is happening and is unable to stop or control it. The subject being tested is asked to follow a penlight or some other object with his or her eye as far to the side as the eye can go. The more intoxicated the person is, the less the eye has to move toward the side before jerking or nystagmus begins. Usually, when a person’s blood-alcohol concentration is in the range of 0.10 percent, the jerking begins before the eyeball has moved 45 degrees to the side

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(see Figure 12–3). Higher blood-alcohol concentration causes jerking at smaller angles. Also, if the suspect has taken a drug that also causes nystagmus (such as phencyclidine, barbiturates, and other depressants), the nystagmus onset angle may occur much earlier than would be expected from alcohol alone.

Walk and turn and the one-leg stand are divided-attention tasks, testing the subject’s abil- ity to comprehend and execute two or more simple instructions at one time. The ability to understand and simultaneously carry out more than two instructions is significantly affected by increasing blood-alcohol levels. Walk and turn requires the suspect to maintain balance while standing heel-to-toe and at the same time listening to and comprehending the test instructions. During the walking stage, the suspect must walk a straight line, touching heel-to-toe for nine steps, then turn around on the line and repeat the process. The one-leg stand requires the sus- pect to maintain balance while standing with heels together listening to the instructions. Dur- ing the balancing stage, the suspect must stand on one foot while holding the other foot several inches off the ground for 30 seconds; simultaneously, the suspect must count out loud during the 30-second time period.

Analysis of Blood for Alcohol Gas chromatography is the approach most widely used by forensic toxicologists for determining alcohol levels in blood. Under proper gas chromatographic conditions, alcohol can be separated from other volatile substances in the blood. By comparing the resultant alcohol peak area to ones obtained from known blood-alcohol standards, the investigator can calculate the alcohol level with a high degree of accuracy (see Figure 12–4).

Eye looking straight ahead

45°

FIGURE 12–3 When a person’s blood-alcohol level is in the range of 0.10 percent, jerking of the eye during the horizontal-gaze nystagmus test begins before the eyeball has moved 45 degrees to the side.

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FIGURE 12–4 A gas chromatogram showing ethyl alcohol (ethanol) in whole blood.

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Another procedure for alcohol analysis involves the oxidation of alcohol to acetalde- hyde. This reaction is carried out in the presence of the enzyme alcohol dehydrogenase and the coenzyme nicotin-amide-adenine dinucleotide (NAD). As the oxidation proceeds, NAD is converted into another chemical species, NADH. The extent of this conversion is measured by a spectrophotometer and is related to alcohol concentration. This approach to blood-alcohol testing is normally associated with instruments used in clinical or hospital settings. Instead, forensic laboratories normally use gas chromatography for determining blood-alcohol content.

Collection and Preservation of Blood Blood must always be drawn under medically acceptable conditions by a qualified individual. A nonalcoholic disinfectant should be applied before the suspect’s skin is penetrated with a ster- ile needle or lancet. It is important to eliminate any possibility that an alcoholic disinfectant could inadvertently contribute to a falsely high blood-alcohol result. Nonalcoholic disinfectants such as aqueous benzalkonium chloride (Zepiran), aqueous mercuric chloride, or povidone-iodine (Betadine) are recommended for this purpose.

Once blood is removed from an individual, it is best preserved sealed in an airtight container after adding an anticoagulant and a preservative. The blood should be stored in a refrigerator until delivery to the toxicology laboratory. The addition of an anticoagulant, such as EDTA or potassium oxalate, prevents clotting; a preservative, such as sodium fluoride, inhibits the growth of microorganisms capable of destroying alcohol.

One study performed to determine the stability of alcohol in blood removed from living in- dividuals found that the most significant factors affecting alcohol’s stability in blood are storage temperature, the presence of a preservative, and the length of storage.3 Not a single blood speci- men examined showed an increase in alcohol level with time. Failure to keep the blood refriger- ated or to add sodium fluoride resulted in a substantial decline in alcohol concentration. Longer storage times also reduced blood-alcohol levels. Hence, failure to adhere to any of the proper preservation requirements for blood works to the benefit of the suspect and to the detriment of society.

The collection of postmortem blood samples for alcohol-level determinations requires added precautions. Ethyl alcohol may be generated in the body of a deceased individual as a result of bacterial action. Therefore, it is best to collect a number of blood samples from different body sites. For example, blood may be removed from the heart and from the femoral vein (in the leg) and cubital vein (in the arm). Each sample should be placed in a clean, airtight container contain- ing an anticoagulant and sodium fluoride preservative and should be refrigerated. Blood-alcohol levels can be attributed solely to alcohol consumption if they are nearly similar in all blood samples collected from the same person. As an alternative to blood collection, the collection of vitreous humor and urine is recommended. Vitreous humor and urine usually do not experience any significant postmortem ethyl alcohol production.

Alcohol and the Law Constitutionally, every state in the United States is charged with establishing and administer- ing statutes regulating the operation of motor vehicles. Although such an arrangement might encourage diverse laws defining permissible blood-alcohol levels, this has not been the case. Both the American Medical Association and the National Safety Council have exerted con- siderable influence in persuading the states to establish uniform and reasonable blood-alcohol standards.

Blood-Alcohol Laws Between 1939 and 1964, 39 states and the District of Columbia enacted legislation that followed the recommendations of the American Medical Association and the National Safety Council in specifying that a person with a blood-alcohol concentration in excess of 0.15 percent w/v

3 G. A. Brown et al., “The Stability of Ethanol in Stored Blood,” Analytica Chemica Acta 66 (1973): 271.

anticoagulant A substance that prevents coagula- tion or clotting of blood.

preservative A substance that stops the growth of microorganisms in blood.

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was to be considered under the influence of alcohol.4 However, continued experimental studies have since shown a clear correlation between drinking and driving impairment for blood-alcohol levels much below 0.15 percent w/v. As a result of these studies, in 1960 the American Medical Association and in 1965 the National Safety Council recommended lowering the presumptive level at which an individual was considered to be under the influence of alcohol to 0.10 percent w/v. In 2000, U.S. federal law established 0.08 percent as the per se blood-alcohol level, meaning that any individual meeting or exceeding this blood-alcohol level shall be deemed intoxicated. No other proof of alcohol impairment is necessary. The 0.08 percent level applies only to non- commercial drivers, as the federal government has set the maximum allowable blood-alcohol concentration for commercial truck and bus drivers at 0.04 percent.

Several Western countries have also set 0.08 percent w/v as the blood-alcohol level above which it is an offense to drive a motor vehicle. Those countries include Canada, Italy, Switzerland, and the United Kingdom. Finland, France, Germany, Ireland, Japan, the Netherlands, and Norway have a 0.05 percent limit. Australian states have adopted a 0.05 percent blood-alcohol concentra- tion level. Sweden has lowered its blood-alcohol concentration limit to 0.02 percent.

As shown in Figure 12–5, one is about four times as likely to become involved in an automo- bile accident at the 0.08 percent level as a sober individual. At the 0.15 percent level, the chances are 25 times as much for involvement in an automobile accident compared to a sober driver. The reader can estimate the relationship of blood-alcohol levels to body weight and the quantity of 80-proof liquor consumed by referring to Figure 12–6.

Constitutional Issues The Fifth Amendment to the U.S. Constitution guarantees all citizens protection against self- incrimination—that is, against being forced to make an admission that would prove one’s own guilt in a legal matter. To prevent a person’s refusal to take a test for alcohol intoxication on the constitutional grounds of self-incrimination, the National Highway Traffic Safety Administration (NHTSA) recommended an “implied consent” law. By 1973, all the states had complied with this recommendation. In accordance with this statute, operating a motor vehicle on a public highway automatically carries with it the stipulation that the driver must either submit to a test for alco- hol intoxication if requested or lose his or her license for some designated period—usually six months to one year.

4 0.15 percent w/v is equivalent to 0.15 grams of alcohol per 100 milliliters of blood, or 150 milligrams per 100 milliliters.

About 25 times as much as normal at 0.15%

.00 .04 .08 .12 .16 .20 Blood-alcohol concentration

About 4 times as much as normal at 0.08%

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FIGURE 12–5 Diagram of increased driving risk in relation to blood-alcohol concentration.

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In 1966, the Supreme Court, in Schmerber v. California,5 addressed the constitutionality of collecting a blood specimen for alcohol testing, as well as for obtaining other types of physi- cal evidence from a suspect without consent. While being treated at a Los Angeles hospital for injuries sustained in an automobile collision, Schmerber was arrested for driving under the influence of alcohol. A physician took a blood sample from Schmerber at the direction of the police, over the objection of the defendant. On appeal to the U.S. Supreme Court, the defen- dant argued that his privilege against self-incrimination had been violated by the introduction of the results of the blood test at his trial. The Court ruled against the defendant, reasoning that the Fifth Amendment only prohibits compelling a suspect to give “testimonial” evidence that may be self-incriminating; being compelled to furnish “physical” evidence, such as fin- gerprints, photographs, measurements, and blood samples, the Court ruled, was not protected by the Fifth Amendment.

The Court also addressed the question of whether Schmerber was subjected to an unreason- able search and seizure by the taking of a blood specimen without a search warrant. In the 1966 decision, the Court upheld the blood removal, reasoning that the natural body elimination of alcohol created an emergency situation allowing for a warrantless search. The Court revisited this issue once again forty-seven years after Schmerber in the case of Missouri v. McNeely.6

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How to Tell What Your Blood Alcohol Level Is after Drinking

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FIGURE 12–6 To use this diagram, lay a straightedge across your weight and the number of ounces of liquor you’ve consumed on an empty or full stomach. The point where the edge hits the right-hand column is your maximum blood-alcohol level. The rate of elimination of alcohol from the bloodstream is approximately 0.015 percent per hour. Therefore, to calculate your actual blood-alcohol level, subtract 0.015 from the number in the right- hand column for each hour from the start of drinking. Source: U.S. Department of Transportation.

5 384 U.S. 757 (1966). 6 133 S. Ct. 932 (2013).

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Here, the Court addressed the issue as to whether the natural elimination of alcohol in blood categorically justifies a warrantless intrusion. The Court noted that advances in com- munication technology now allow police to obtain warrant quickly by phone, e-mail, or teleconferencing.

In those drunk-driving investigations where police officers can reasonably obtain a warrant before a blood sample can be drawn without significantly undermining the efficacy of the search, the Fourth Amendment mandates that they do so. . . . In short, while the natural dissipation of alcohol in the blood may support a finding of exigency in a specific case, as it did in Schmerber, it does not do so categorically. Whether a warrantless blood test of a drunk-driving suspect is reasonable must be determined case by case based on the totality of the circumstances.

The Role of the Toxicologist Once the forensic toxicologist ventures beyond the analysis of alcohol, he or she encounters an encyclopedic maze of drugs and poisons. Even a cursory discussion of the problems and handi- caps imposed on toxicologists is enough to develop a sense of appreciation for their accomplish- ments and ingenuity.

Challenges Facing the Toxicologist The toxicologist is presented with body fluids and/or organs and asked to examine them for the presence of drugs and poisons. If he or she is fortunate, which is not often, some clue to the type of toxic substance present may develop from the victim’s symptoms, a postmortem patho- logical examination, an examination of the victim’s personal effects, or the nearby presence of empty drug containers or household chemicals. Without such supportive information, the toxicologist must use general screening procedures with the hope of narrowing thousands of possibilities to one.