How accurate are breath tests?

On Behalf of | Jun 25, 2020 | Criminal Defense |

When police pull someone over under suspicion of drunk driving, their first step is often to conduct a field sobriety test. This process frequently includes a breath test.

The first device that tested breath for alcohol was developed in 1938. Since then, companies created several types and brands of breath tests, such as the Breathalyzer.

Breath tests are a common tool in DUI traffic stops but a common question remains: How accurate are they?

How do breath tests work?

The legal limit of BAC in North Carolina is 0.08%, like most other states. If a breath test determines someone’s BAC is at or above that level, then police have reasonable cause to arrest them.

However, the breath test is only an estimate of BAC. And they have a questionable reputation. This is because various other factors can influence the result of a breath test, including:

  • An individual’s physical condition, such as their natural body temperature
  • Other substances they have consumed, even prescription medications
  • Recently smoking a cigarette

Additionally, breath tests can occasionally detect alcohol up to 24 hours after individuals consume it. Alcohol can stay in one’s system for a considerable amount of time, depending on several factors, but after 24 hours, most people are no longer impaired.

So, are breath tests reliable?

Unfortunately, there is no definitive answer to this question. Several studies over the years found that breath test results can vary up to 15% of the actual BAC – and that result is often higher as well.

Yet, if breath tests were extremely inaccurate, police all across the country would likely not use them. And, as time goes by and technology improves, breath tests may become more accurate.

However, it is important to note that the results of any breath tests are not permitted in court. Courts do not allow them as evidence.

Individuals can dispute the results of a breath test long before they go to court. That is why it is critical for individuals to consult an experienced defense attorney to determine how they can protect their rights and what steps they should take next.