Blood tests vs. breath tests: Measuring reliability

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Variations in breath test readings and blood test results have caused people to question the accuracy of breath analyzers.

Many people enjoy having drinks when going out with friends or having dinner. However, when people choose to climb behind the wheel of a vehicle after drinking, they run the risk of getting pulled over by a California law enforcement officer. Officers use a variety of tests to establish whether a driver has an alcohol content level that would impair their ability to drive or is equal to or above the legal limit of 0.08 percent. Although blood tests are the most accurate way to make this determination, it is difficult to administer these tests on the side of the road. Instead, breath test analyzers are used to convert the amount of ethanol alcohol contained in the driver's exhaled breath sample into a blood alcohol content level.

Discrepancies in breath test readings and blood test results have led many people to question the accuracy of breath analyzer machines. According to the State University of New York at Potsdam, the results of breath tests and blood tests can differ by as much as 15 percent, which is significant. In fact, this variation in results may cause a person to be arrested and charged with a DUI who may not have otherwise been arrested and charged.

Measuring BAC from a breath sample

When drivers blow into a tube that is connected to the breath test device, the machine detects how much ethanol alcohol is in the sample. It then uses the same formula to convert this concentration of alcohol into a BAC level for every individual, even though blood chemistry and metabolism varies to some degree with the individual. Rather than measure just the ethanol alcohol, it is possible the machine may pick up other similar molecular substances in the subject's mouth and in the environment. These compounds can also sway the accuracy of the results. Even some medical conditions, as well as the proper use, calibration and maintenance of the equipment by qualified individuals, can affect breath test results.

For example, a study participant, who worked with contact cement and paint for a total of an hour, was asked to give a breath sample 20 minutes after finishing the tasks. Surprisingly, the BAC level obtained from the breath analyzer measured 0.12 percent, while the actual BAC level received from a blood sample was zero.

Blood samples are available by the Defendant for retest and analysis, while breath samples are not captured and preserved.

Finding legal representation

A DUI conviction can affect a person's life in many ways. It can affect employment, licensing, and a number of areas in a person's life. A DUI defense attorney in California can give you a realistic appraisal of your case and the best way to proceed after reviewing everything, including testing, the contact with law enforcement, and other personal and case related factors.

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