Currently, the USA transport sector is marred with drunk driving, which usually leads to deaths, property destruction, and permanent injury. Despite numerous campaigns to curb the menace, many drivers still use alcohol or other drugs while driving their vehicles. Therefore, the National Highway Transportation Safety Administration (NHTSA) devised three sobriety tests to help the police department determine if the road users are sober (Levine, 2013). The three tests include; the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test.
The horizontal gaze nystagmus test is one of the commonly used sobriety tests today. It determines if an individual is impaired by alcohol consumption. It is mainly composed of horizontal gaze nystagmus (HGN), an involuntary arhythmic of an individual’s eye upon gazing to the side (Levine, 2013). Consumption of alcohol exaggerates the jerking of the eye; hence it demonstrates impairment. Since alcohol inhibits the nervous system’s function, its effect is felt on a person’s incapability to regulate sideways eye movements accurately and smoothly (Powers & Dean, 2015). Moreover, those who show the exaggerated jerking of the eyes are not aware of their state. When asking a suspect to perform these tests, the police usually look for the start of nystagmus before angle 45, limited smooth pursuit, and different nystagmus at maximum deviation (Bell et al., 2019). Therefore, any show of these behaviors illustrates that the suspect is under the influence of the drug.
The walk and turn test is also a sobriety test that the police officers usually perform on the suspects to determine if the individuals are under alcohol influence. It is generally divided into stages and sometimes referred to as a nine-step test. Usually, the suspect is directed to walk nine steps in a straight line using the heel-to-toe steps. After completing the walk in the forward direction, the suspect is asked to return in the opposite direction using the same manner. The test is divided attention in that it focuses on the physical and mental tasks (Bell et al., 2019). The police are usually looking for eight indicators on the suspect to determine the rate of impairment. They include: if the suspect uses arms to balance, steps off the line, miniating the balance during the instructions, does not touch heel-to-toe, starts too soon, takes an inaccurate number of steps, performs improper turns, and finally, when the individual stops while walking. In case the patient exhibits these characters, then they are regarded as drunk and can be prosecuted.
Lastly, during the one-leg stand test, the suspect is usually asked by the administering police to stand on one foot, and the official counts in thousands for approximately 30 seconds. The suspects are generally required to have their arms by their side, and their eyes should be kept on the high foot. Accord to Powers and Dean (2015), a one-leg stand is estimated to be more than average inaccuracy of revealing if the suspect is under the influence of alcohol. Usually, the police are looking for hops, putting the foot down, sways, and use of arms to balance. Therefore, if the suspected shows any of these signs, then they are considered to be under influence of a substance.
In conclusion, the three tests that NHTSA devised have aided the police in identifying the drunk drivers. The horizontal gaze nystagmus test determines the exaggeration of the eyes’ jerking while walk and the turn test assess the level of concentration. However, the one-leg stand test shows the stability of the suspect. Being that alcohol interferes with the nervous system, it can lower an individual’s ability to be stable. Although the sobriety tests are not 100 % accurate, they are above average hence an effective indicator in determining the level of drug use.
Reference
Bell, S., James, S., & Nordby, J. J. (2019). Forensic science: An introduction to scientific and investigative techniques (5th ed.). CRC Press.
Levine, B. (2013). Principles of Forensic Toxicology (4th ed.). American Association for Clinical Chemistry Press.
Powers, R. H., & Dean, D. E. (2015). Forensic toxicology: Mechanisms and pathology. CRC Press.