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Are Blood & Breath Tests Always Accurate?

Are Blood & Breath Tests Always Accurate?

When you are arrested on suspicion of driving while under the influence (DUI), you will be required to take a breath or blood test to determine your blood alcohol content (BAC) level. While this technology has come a long way and is more accurate now than perhaps it has ever been before, many people often don’t realize how common errors actually are in making this determination.

For starters, the type of blood or breath sample analyzer is not standardized by any means. Different law enforcement agencies use different systems based on the contracts they sign, the agreements they make, and based on what’s available to them at the time. This leads to some potentially large discrepancies since each of them function differently and use different methods and technology to come to their conclusions. As a result, you may be surprised to learn how inaccurate the evidence presented against you may actually be.

Margin of Error

Even if a machine has been properly calibrated and has been shown to be working properly, studies have shown that these machines have a considerable margin of error. Conservative studies estimate that your reading could be off by as much as 15%, while others have increased that number to as much as a whopping 23% difference! 23% could make the difference between you blowing a .08% and a .06%; one of these could convict you while the other is well under the legal limit.

And that’s assuming the machine is working properly. If the calibration is off at all, the margin of error can jump even higher, meaning this evidence that was collected to show your guilt is essentially useless and proves nothing. Machine calibration is a tricky process and humans are not perfect. In fact, human error plays a surprisingly large role in DUI cases.

Breath tests are even worse for accuracy than blood tests. The Wisconsin State Laboratory of Hygiene found that only 33% of all breath test results matched the results of a corresponding blood test. What does this mean for your case? You should not hesitate to let an attorney review the evidence on your behalf and determine if error, either human or inherent, may be contributing to the case against you.

Factors to Consider

Speaking of human error, what other mistakes can make a blood or breath test invalid? Procedures for administering these tests are highly-standardized to obtain maximum accuracy. Any deviation from these procedures could invalidate your test results, leading to the evidence being suppressed.

While breath tests are commonly used and often inaccurate, blood tests are generally less error-prone. However, they require quick analysis. If a blood sample were to sit too long without being tested, the results will change. Blood decomposes or congeals over time, which then increases the concentration of the alcohol within it, making your sample appear to contain a higher percentage of alcohol than it did at the time it was taken. You should allow an attorney who is experienced in handling and analyzing this evidence review your case for you in order to find any discrepancies that may have emerged.

At Skousen & Reedy, PLC, we understand how frightening and stressful a DUI arrest can be. We understand that one mistake shouldn’t impact you for the rest of your life, and we take pride in providing all of our clients with top-quality, aggressive representation. We are your loyal advocates throughout your case, and can represent you through both your criminal case and your administrative hearing. Our reputation of success both in and out of the courtroom speaks for itself, including having been named one of the 10 Best in Client Satisfaction for two consecutive years by the American Institute of DUI/DWI Attorneys™.

Call Skousen & Reedy, PLC today at 480-889-8909 to schedule a consultation and obtain high-quality defense for your DUI case!


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