Tuesday, April 21, 2009

Challenging the Breath Test in Court

A breathalyzer or breath test result showing a blood alcohol concentration (BAC) over the legal limit can be one of the most damaging pieces of evidence in the context of a driving while intoxicated (DWI) or driving under the influence (DUI) trial. Though damaging, however, breathalyzer evidence is not ironclad. A variety of factors may cause false or inaccurate readings, allowing DWI defense lawyers to challenge their reliability in court.

Common ways to dispute breathalyzer test results include:

Calibration Error

Like any machine, breathalyzers degrade and become less sensitive over time. Proper calibration is needed to ensure that results are accurate. Evidence that a machine was not properly adjusted and/or maintained may discredit its results.

Operator Qualifications

In most states, strict laws are in place to regulate the operation and maintenance of breath test machines. Because these devices are very sensitive, operators must be properly trained to adapt to different environmental, biological, and physical circumstances. A test administered by an untrained police officer may produce inaccurate or unreliable readings.

Absorption Defense

The absorption of alcohol into the bloodstream takes time. By some estimates, it may take up to two hours for consumed alcohol to reach equilibrium distribution throughout the body. Breathalyzer tests administered during this period can produce inaccurate results, since alcohol content is inconsistent in different areas of the body. Furthermore, if alcohol has not yet been absorbed into the bloodstream, it does not contribute to a person's level of intoxication.

Biological Variables

Breath test results are based on a standard mathematical formula which relates the amount of alcohol on a person's breath with the amount of alcohol present in their bloodstream. This formula, however, only applies when all biological variables conform to its standards. The ratio of breath alcohol to blood alcohol varies between individuals and over time; variations in body temperature can also affect results.

Summary

All in all, there are many ways in which breathalyzer tests can produce inaccurate or misleading results, leading to situations where defendants can and should challenge this evidence in court.

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Driving While Intoxicated

Driving while intoxicated is the act of operating and/or driving a motor vehicle while under the influence of alcohol and/or drugs to the degree that mental and motor skills are impaired. It is illegal in all jurisdictions within the U.S. The specific criminal offense is usually called driving under the influence (of alcohol and/or other drugs, DUI), and in some states driving while intoxicated (DWI), operating while impaired (OWI), or operating a vehicle under the influence (OVI). Such laws may also apply to boating or piloting aircraft.

In the United States the National Highway Traffic Safety Administration (NHTSA) estimates that 17,941 people died in 2006 in "alcohol-related" collisions, representing 40 percent of total traffic deaths in the US. Over 500,000 people were injured in alcohol-related accidents in the US in 2003. NHTSA defines fatal collisions as "alcohol-related" if they believe the driver, a passenger, or an occupant of the vehicle (such as a pedestrian or pedalcyclist) had a blood alcohol content (BAC) of 0.01 or greater. NHTSA defines nonfatal collisions as "alcohol-related" if the accident report indicates evidence of alcohol present. NHTSA specifically notes that "alcohol-related" does not necessarily mean a driver or nonoccupant was tested for alcohol and that the term does not indicate a collision or fatality was caused by the presence of alcohol. On average, about 60 percent of the BAC values are missing or unknown. To analyze what they believe is the complete data, statisticians simulate BAC information. Drivers with a BAC of 0.10 are 6 to 12 times more likely to get into a fatal crash or injury then drivers with no alcohol.