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Circadian rhythm may play a role in field sobriety tests

Posted by Craig Penrod | Feb 04, 2014 | 0 Comments

Most driving under the influence (DUI) arrests take place at night, many of them during traffic stops well after midnight in Tempe, Phoenix or other communities in Maricopa County.

It is well known that many law enforcement officers engage in a process often referred to as "cherry picking," which is the practice of staking out bars and restaurants starting about 10 p.m. to "closing time" at around 2 a.m. and then pulling cars over on some pretext as patrons proceed to drive to their next destination.

In Tempe, Phoenix or other communities in Maricopa County, it is important that you consult experienced Arizona DUI lawyers like those associated with the Law Offices of Craig W. Penrod, P.C.

A field sobriety test that is commonly administered to driver's who are suspected of DUI is the horizontal gaze nystagmus (HGN). Gaze nystagmus is a type of jerk nystagmus where the eye gazing upon or following an object begin to lag and the eye attempts to correct itself with a saccadic movement toward the direction in which the eye is moving or gazing.

An eye normally moves smoothly like a marble rolling over a glass plane, whereas an eye with jerk nystagmus moves like a marble rolling across sandpaper. Most types of nystagmus, including HGN, are involuntary motions, meaning the person exhibiting the nystagmus cannot control it. In fact, the subject exhibiting the nystagmus is unaware that it is happening because the bouncing of the eye does not affect the subject's vision.

One claim of impaired drivers exhibiting HGN is that fatigue and not alcohol is the cause of their impairment. National Highway Traffic Safety Administration (NHTSA) studies have shown that fatigue has no significant effect on the manifestation of HGN. However, it is during this late night period of time that the circadian rhythm of individuals may be taking effect. Circadian rhythm is the 24-hour biological alarm clock in our minds and bodies. A prime example is the experience jet lag caused by changing time zones.

A circadian rhythm is defined any biological process that displays an oscillation of about 24 hours. These rhythms have been widely observed in plants, animals, fungi and cyanobacteria. The term circadian comes from the Latin circa, meaning around or approximately, while diem or dies, means day. Although circadian rhythms are built-in or self-sustained, they are adjusted to the local environment by external cues, the most important of which may be daylight.

Research has shown that individuals perform poorly in tests that are administered during the low point of a person's circadian rhythm, that is, during the hours after midnight and into the early morning. Unfortunately, field sobriety tests (FSTs) used by law enforcement officers in an attempt to determine whether a driver is intoxicated or not are usually administered when a person is destined to perform poorly.

British physicians and psychiatrists have reported in a study titled "Circadian Variation in Effects of Ethanol in Man" that "the same blood alcohol level is associated with a significantly greater impairment of different aspects of psychological functioning when achieved in the morning."

These researchers concluded that "the differences we have found (in field sobriety test performances)…must be attributable to circadian change and susceptibility of the body to its effect."A study published in the Journal of Vestibular Research, concluded that "oculomotor function clearly decreased after sleep deprivation, but the performance deteriorations were complex and not necessarily correlated with subjectively felt sleepiness."

This issue is one of several very complicated matters that can lead to a conviction for DUI in the state of Arizona and elsewhere. It is important that your DUI legal situation should be handled by expert professionals with the experience possessed by the attorneys at the Law Offices of Craig W. Penrod, P.C. Our office offers free consultations for all DUI and criminal matters. Our Arizona DUI attorneys and Arizona criminal lawyers can provide you with the experience and knowledge needed for qualified representation. An experienced Arizona DUI lawyer is vital in DUI cases and our DUI attorneys set that standard. If you're in need of a criminal defense, our Arizona criminal attorneys are ready to assist you.

About the Author

Craig Penrod

Craig W. Penrod was born and raised in Arizona and has practiced criminal defense for over 30 years. Mr. Penrod is a member of the State Bar of Arizona, Maricopa County Bar Association, State of Nevada Bar Association, American Bar Association, American Trial Lawyers Association, Arizona Trial Lawyers Association, Nevada Trial Lawyers Association, Arizona Attorneys for Criminal Justice and the National Association of Criminal Defense Lawyers.

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