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How Accurate are DUI Chemical Tests?

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How Accurate are DUI Chemical Tests?


When you’re arrested and charged with driving under the influence of drugs or alcohol, you are required to submit to a chemical test to determine your intoxication level. Naturally, as someone who is expecting a fair trial, you would expect the evidence obtained this way to have integrity and be free from defects or outside factors that could influence the results against you. This brings up a fairly interesting question: are these tests actually accurate?

The answer may surprise you: you may not realize just how wildly inaccurate a chemical test could be, particularly if testing procedures and protocols aren’t followed correctly. On this blog, our Reno DUI lawyer will discuss a few of the ways in which your test could be flawed and your results inaccurate, thus calling into question the legitimacy of the evidence.

Three Types of Chemical Tests

There are three types of chemical tests that authorities can use for the purposes of determining your intoxication level: blood, breath, and urine. For drug-related DUI charges, only blood and urine tests can be used since breathalyzers aren’t capable of picking up traces of intoxicating compounds, like THC from marijuana. Instead, breathalyzers can only be used for alcohol-related DUI charges.

Inherently, there are some issues with each type of test that could jeopardize its accuracy. Let’s look at them a little bit further.

Blood Tests

Blood tests are often not the method of testing that law enforcement prefer to use. For starters, it’s invasive, and requires a lot of care and caution in order to properly test someone. If someone is acting intoxicated, properly administering a blood test can be immensely difficult. Assuming the blood samples are drawn properly, the samples must be handled carefully and sent to a laboratory for testing. During transport, the samples must be kept at a constant temperature, must avoid being heavily shaken or disturbed, and plenty of other requirements must be met as well. In short: a lot can go wrong.

Blood tests also usually take anywhere from a few days to a week or so to get results back, by which time you’ll have needed to get a considerable amount of preparation done for your case. As such, both sides usually agree this isn’t the ideal way of testing for intoxication.

Urine Tests

Urine tests are disliked for many of the same reasons that blood tests aren’t preferred: they’re invasive, require laboratory testing, and in many cases highly unsanitary, requiring careful handling. While these tests are often preferred by people who wish to avoid being stuck with a needle, they are also notoriously less accurate than blood tests as well, particularly at determining the current amount of a substance in the body. Even if someone was previously intoxicated and has waited until they “sobered up” before driving, their urine test could still contain immense amounts of alcohol because their liver has cleaned it up and your body is waiting to dispose of it.

Urine tests may also show illegal amounts of drug intoxicants for as much as several days or even weeks after the drug use occurred and the intoxication has passed. Both of these factors could contribute to evidence against someone being inconclusive.

Breath Tests

Breath tests are the preferred method of chemical testing for alcohol-induced intoxication. These tests are non-invasive, quick to conduct, inexpensive, simple, and usually yield pretty accurate results as long as standard protocols are followed.

However, as with the other two tests, they’re also not perfect. Breath tests could be swayed heavily by mouth alcohol, which is traces of alcohol still in your mouth that have not yet been absorbed by your body (and thus, can’t contribute to your intoxication levels). Mouth alcohol can cause someone who is not intoxicated to blow a breathalyzer test that’s over the legal limit, even though they’ve never committed a crime.

Furthermore, breathalyzer machines need to be properly calibrated to work correctly and yield accurate results, and improper maintenance or poor calibration can throw all of the evidence collected against you into question, possibly even resulting in it being thrown out.

Talk to a Reno DUI attorney from the Law Offices of Kenneth A. Stover today by dialing (775) 502-1575 if you have been arrested and charged with driving under the influence.
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