James E Smith Steven I Dworkin

High school students Mary Herz and Mitch Sutherland take a mandatory Breathalyzer test from principal George Yerger before entering the prom in Grant, Nebraska, May 3, 1997. (AP Photo/George Hipple)

BREATHALYZER Breath-analysis machines detect and measure the ALCOHOL present in deep lung air and convert this to an estimate of Blood Alcohol Concentration (BAC). The basis for this calculation is the relatively constant though small proportion of alcohol that the body excretes through the lungs. BAC is approximately 2,300 times breath alcohol concentration, although there is some variation among individuals. Breath analysis machines use methods such as thermal conductivity and infrared absorption to detect alcohol in lung air. Because breath alcohol analysis is quick and non-invasive, it is a useful tool in a variety of situations. The breathalyzer has traditionally been associated with law enforcement agencies for monitoring drinking and driving. However, it is increasingly being used in clinical sellings. A number of models—both portable and fixed ones—are available.

The Breathalyzer breath test machine is the tradename of the model manufactured by Smith and Wesson, but the name has become synonymous with breath test machines. It has emerged as a powerful tool for law enforcement officers in policing motorists who are operating motor vehicles while under the influence of illegal levels of alcohol.

Officers routinely conduct field sobriety tests on motorists they suspect of driving while intoxicated. An officer first requests that the motorist suspected of intoxication perform certain physical tests, such as walking a straight line, putting a finger to the nose, or balancing on one foot, in order to corroborate the officer's conclusion of intoxication of the motorist based on objective findings. If the officer concludes that the motorist has failed one or more of these tests, the officer requests that the motorist submit to a Breathalyzer test. The results of the test either bolster and corroborate police opinion testimony of intoxication or, in those states that set presumptive blood alcohol intoxication levels, to demonstrate that the motorist's blood alcohol level exceeded the permissible level.

If a motorist refuses to take a breathalyzer test, the police cannot compel the person to take the test. However, states have enacted implied consent laws that are civil, rather than criminal, in nature. Under these laws, if a motorist refuses to take the breathalyzer test, the motorist's driver's license is automatically suspended for a set period of time. Thus, motorists who are confronted with the alternatives must balance the criminal sanctions that follow a high alcohol reading from the breathalyzer against the immediate suspension of their driving privileges. However, in the late 1990s, some states, including New York and California, enacted laws that made refusing a breathalyzer test a crime. In these and several other states, legislators concluded that a license suspension was not a severe enough penalty for drunk drivers.

Because breathalyzer test results serve as powerful incriminating evidence, defendants and their lawyers often seek to challenge the reliability of the tests. This has produced a group of experts that routinely testify as to the way the test was administered and the reliability of the breathalyzer machine itself. The breathalyzer must be calibrated periodically. Calibration is a procedure performed by laboratory personnel to ensure the accuracy and reliability of the instrument. Routine maintenance is also performed to ensure the continued accuracy and proper function of the breathalyzer. Once calibrated, a certificate of calibration is completed by the laboratory and a certified copy provided to the law enforcement agency using that breathalyzer. Failure to follow maintenance schedules can raise a reasonable doubt about the machine s results and lead to an acquittal. Apart from the alleged technical defects of a breathalyzer, experts often testify that the officer failed to follow the proper protocol for operating the machine or that the defendant s blood alcohol level was incorrectly inflated due to biological factors.

Breathalyzers are also being used as preventive devices. Courts are now ordering persons convicted of repeat driving while intoxicated violations to install a breathalyzer interlock on their cars. The driver must breathe into the machine before starting the car. If the alcohol level is too high, the car will not start. After the car has started, the driver must periodically breathe into the device for a retest. If the driver fails the test, the car honks its horn and flashes its lights.

(SEE ALSO: Driving Under the Influence; Drunk Driving)


Giles, H. G., ET AL. (1990). Alcohol and the identification of alcoholics. Lexington and Toronto: D. C. Heath.

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