Most drunk driving arrests take place at night, often after midnight. One reason for this is that many police officers engage in â€œcherry pickingâ€ â€” that is, the illegal practice of staking out bars and restaurants around closing time and pulling cars over on some pretext as patrons leave and drive away.
It is during this period of time that the individualâ€™s circadian rhythm is taking effect.
The circadian rhythm is that 24-hour biological alarm clock in each of our bodies, most noticeable when we experience â€œjet lagâ€. Researchers have found that individuals will perform more poorly in tests during the low point of the circadian rhythm â€” that is, during the hours after midnight and into the early morning. It is just such tests â€” field sobriety tests â€” that officers use to determine whether a driver is intoxicated or not.
Specifically, British physicians and psychiatrists reported that â€œthe same blood alcohol level is associated with a significantly greater impairment of different aspects of psychological funtioning when achieved in the morning.â€ â€œCircadian Variation in Effects of Ethanol in Manâ€, 18 (Supp. 1) Pharmacology, Biochemistry and Behavior 555.
The researchers concluded that â€œthe differences we have foundâ€¦must be attributable to circadian change and susceptibility of the body to its effect.â€