Sobriety Testing

Sobriety is defined as a physiological and mental state in which a person is unaffected by the presence of a chemical substance. The quintessential example of sobriety is the popular image of a return to an individual's normal behavior after the effects of excessive alcohol consumption have dissipated.

The possibility of alcohol or other intoxicants in a crime, accident, or death is uppermost on the mind of a forensic investigator. In 2002, for example, almost 17,500 motorists were killed in alcohol-related traffic accidents in the United States, according to statistics from the U.S. National Highway Traffic Safety Administration. While the involvement of alcohol in traffic fatalities has been declining in the United States since the 1980s, this fatality toll still represented 41% of all U.S. traffic fatalities.

Alcohol-fueled domestic disturbances can also result in injury and death. Crime Report statistics complied in the late 1980s by the State of New Jersey, and reports examining telephone calls to domestic hotlines indicate that at least 40–50% of domestic disturbances were correlated with abusive behavior linked to the use of alcohol. Sobriety testing is not just a factor in alcohol use. While the term sobriety is commonly linked with the consumption of alcohol, the misuse or overuse of prescription drugs and the use of illicit drugs also affect sobriety.

Thus, when responding to a report of a traffic accident (or even stopping a motorist for a suspected traffic infraction) or other incident, police officers can be confronted with need to establish the sobriety of an individual.

Aside from safety issues (operation of a motor vehicle while impaired), sobriety testing is another piece of forensic evidence in the investigation of a crime, accident, or death. Sobriety testing involves the recognition of key indicators of impairment, assessment of physical coordination, and the level of ethanol or drugs in the bloodstream.

This assessment begins as soon as the police officer or forensic investigator encounters the person. For example, police officers are trained to inhale when the driver of a vehicle rolls down the window. Use of alcohol, marijuana, and phencyclidine (PCP, also known popularly as angel dust) can be evident on a person's breath. This is also an opportunity for a brief visual inspection of the inside of the vehicle. Open or discarded bottles or cans of alcohol, aside from being illegal in many jurisdictions, can indicate over-consumption, and are grounds for conducting more rigorous sobriety testing.

Another immediate aspect of sobriety testing is the observance of physical appearance and behavior. A red-appearing face, especially the cheeks, can be caused by the overuse of alcohol, which can increase the flow of blood through the capillaries.

Behavioral changes depend on the nature of the intoxicant. Alcohol is a depressant, as are barbiturates , sleeping pills, and benzodiazepines. Impairment can be evident as slurred or thick speech, sluggish reactions, features of exhaustion such as yawning and drooping of the eyes, and disorientation with surroundings and events.

Some of the behaviors, such as speech difficulties and disorientation, can also be present when impairment is due to narcotics and inhalants (e.g., vapors produced by solvents like nail polish remover and gasoline or adhesives like airplane glue). Drugs like cocaine stimulate the activity of the central nervous system. The result can be euphoric behavior. This also occurs when narcotics and PCP are taken.

A key early sobriety test is examination of the pupils of the eyes. A police officer will typically make direct eye contact with a driver, even asking the driver to remove sunglasses if necessary. Bloodshot eyes and droopy eyelids can be indicative of alcohol overuse. The use of stimulants, hallucinogens, and inhalants can cause the pupils to be become larger than is normal for the light conditions (dilation). In contrast, narcotics such as codeine, heroin, and opium cause the pupils to become smaller (constriction). A blank or dazed stare can result from the use of PCP, hallucinogens, and inhalants.

If the early assessment of sobriety warrants further action, a police officer or forensic investigator can conduct more rigorous tests.

One standard sobriety test is the indirect measurement of the level of alcohol in the blood by measurement of the alcohol in the expired breath. A portable Breathalyzer displays the level of alcohol as a number that indicates the grams of alcohol per 100 milliliters of blood. In many jurisdictions, this legal limit is 0.08. If the breathalyzer reading exceeds this value, it is evidence that the person may be impaired.

Other sobriety tests typically adhere to a standard field sobriety testing program. Use of established guidelines lessens the chances that the results of the tests will be questioned in court, even in the absence of a Breathalyzer® test, and allows the test results to be the basis of an arrest for driving while intoxicated (DWI) or driving under the influence (DUI).

Standardized Field Sobriety Tests (SFST) were developed in the 1970s by the U.S. National Highway Traffic Safety Administration. The validity of the testing methods and legality of the results was verified by repeated testing under controlled conditions. Without the power of this standardizing procedure, sobriety tests can be merely anecdotal and so less apt to stand legal scrutiny.

SFST involve scoring of the results of a number of requested actions. A determination of intoxication is made if a person fails to successfully perform a sufficient number of these actions: the walk-and-turn, one-leg-stand, and horizontal-gaze nystagmus (eyemovement) tests, which are detailed below. Failing a single test is not grounds for determining that a person is not sober.

The walking and leg-stand tests are assessments of balance, while the eye movement test assesses motor control of the eye muscles. All are tests of coordinated action of muscles and nerve activity. However, the legal admissibility of the first two tests can be challenged more successfully than the eye test. This is because the assessment of walking and standing abilities are more subjective. The eye muscle control that is the basis of the horizontal gaze test is involuntary, and so is able to be assessed more definitively.

Nystagmus is defined as an involuntary rapid and repetitive movement of the eyes. It can occur as a result of brain damage, epilepsy , or other pathological disorders. However, for the majority of people, the condition is indicative of impaired motor function. Normally, when concentration and the nervous system are unimpaired, movement is followed by a smooth and controlled change in gaze. However, a sign of impairment can be the loss of this coordinated activity.

Typically, a subject is asked to look straight ahead and, while keeping the head still, to focus on a horizontally moving object (a finger, pen, or pencil, for example). The object must be 12–15 inches from the subject's eyes, at a distance that the subject indicates is comfortable to focus.

People with an eye impairment or an artificial eye are excluded from the test. Evaluating a single eye and then doubling the score with the assumption that the other eye will behave in the same manner is improper technique. Some people do exhibit a difference in the reaction times of their eyes (a condition called lazy eye). In this case, each eye should be tested separately while the other eye is covered.

A normal eye reaction in this test includes the smooth movement of the pupil from side to side while maintaining focus on the moving object. As well, the pupil should remain still when the object is brought to rest at the end of a leftward or rightward horizontal path. The object can also be moved up or down, to assess if the pupil tracks smoothly.

The side-to-side and up-and-down motions of the object are done a total of at least six times. A score of one is assessed if eye motion in an individual trial is jerky. A score of four or more is indicative of intoxication.

In the walk-and-turn assessment, a reasonably straight line is drawn on a flat surface. The subject is then instructed to place their left foot on the line and then to walk heel-to-toe along the length of the line, by placing the heel of one foot in contact with the toe of the planted foot. In this way the feet remain close together, and balance becomes critical in maintaining progression along the line. When reaching the end of the line, the subject must turn around while keeping one foot planted and repeat the walk in the other direction.

Indications of intoxication include loss of balance (swaying or falling), holding the arms out from the body to maintain balance, stopping and starting rather than walking with a smooth cadence, stepping off of the line, failure to listen to instructions, and starting to walk before being instructed to do so. These aspects of performance are evaluated, scored, and used to assess if coordination is impaired.

For people aged less than 65, who are not judged to be obese, and who do not have a neurological or other disorder that affects balance, another assessment of balance involves standing motionless on one leg. The raised leg must be positioned in front of the body at least six inches off the ground for a time that is determined by the assessor. Swaying, falling, hopping, use of arms for balance, and putting the elevated leg down prematurely are all indications of impairment.

see also Automobile accidents; Breathalyzer®; First responders.