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How Reliable Are Crime Lab BAC Tests?

Many individuals incorrectly believe that if the lab sends back results which indicate that your blood-alcohol content (BAC) was above the legal limit, that should be considered 100% conclusive evidence. However, the fact that the crime lab says you had a certain blood-alcohol content level, does not guarantee that you actually did. As with any lab test, BAC tests at crime labs always carry a certain probability of yielding a false positive or a false negative.

Even blood tests, which are considered the most accurate of BAC tests, are still subject to some possibility of error. Most of the time incorrect results from the crime lab are caused by human error. These mistakes could be things like poor chemistry practices at the lab, improper blood preservation, and contamination of the sample. A good DUI defense lawyer can discover problems with the crime labs procedures and other issues that could affect the validity of the test results.

Common Reasons for False Positives

  • Poor Record Keeping – Some crime labs handle hundreds of tests on a weekly basis. While getting the tests mixed up may sound far-fetched, it’s actually an easy mistake to make when poor record keeping is at play.

  • Bad Sample – Blood which has been sitting around for a long time or was not properly preserved after the sample was taken can coagulate. Coagulated blood may sometimes lead to an artificially high result when measuring BAC. Typically, crime labs process samples in a timely manner. However, bad organization or an overloaded crime lab may end up causing your sample to sit around for too long before it’s tested.

  • Less Accurate Tests – Some tests are more accurate than others. Urine and breath tests are much less accurate than blood tests. If a crime lab analyzes your urine to determine BAC, it’s much more likely to yield inaccurate results and false positives. Even simple things like not urinating for a while before having the urine sample taken can lead to artificially high results.

Lab tests are usually accurate. However, you should remember that inaccurate results are still possible. An experienced Washington DUI attorney can help you bring into question the accuracy of your test results. Call Murphy’s Law Offices today at (253) 312-6122 to get a free consultation.

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Murphy’s Law Offices
506 S. 11th St.
Tacoma, WA 98402
Phone: (253) 312-6122

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