Issues With Breathalyzers in Virginia DUI Cases

Although breathalyzer results are commonly presented as evidence in DUI cases, there are a number of issues that breathalyzers can present. Below, a Virginia DUI lawyer discusses these issues and the impact they can have in court. For information regarding your case, call and schedule a consultation today.

What Are Some Ways That Breathalyzers Can Result in False Positives?

The main way that a breathalyzer gives a false positive or an inaccurately high BAC score is through mouth alcohol. In other words, when a person drinks alcohol, some of that alcohol will remain in their mouth for up to half hour after they’re finished drinking. In addition, if a person burps or even vomits, that can introduce alcohol back in to the mouth.

Therefore, if there has not been a waiting period prior to the BAC test of at least 20 minutes or up to a half hour, then there can be a false positive or inaccurately high reading because the machine is detecting the alcohol in the mouth rather than the alcohol that is coming from the lungs.

Accuracy of Breathalyzers

Breathalyzer machines have to be regularly calibrated and maintained. The records of when the calibrations were done, and by whom, are kept by the Virginia Department of Forensic Science. If calibrations are not done regularly and are not done properly, then the machine can be inaccurate. Even where is proper and timely calibration, some machines will go out of calibration before their next tune-up.

By getting the log of all of the breath tests that were done on the same day as the accused from the Department of Forensic Science, a lawyer in conjunction with a forensic scientist can look at the various results and the various differences in results to determine whether the machine was accurate enough to provide a result that can then be used in court.

How Often Do Breathalyzer Machines Need to Be Calibrated?

A breathalyzer machine in Virginia self-calibrates literally before and after every test. Routine maintenance is also important.

If There Are Issues Why Are Breathalyzers Continued To Be Used?

The government experts are aware of the issues with the breathalyzer machines. They continue to use them, first of all, because it would be very expensive to replace all of them with the new technology. In some cases, it’s because there’s not better technology available. But probably the reason that they continue to use them in most cases is because the courts accept them. In most cases, a blood alcohol test that is introduced into evidence will be sufficient evidence at trial to show that the person was under the influence.

Can You Challenge a Breathalyzer Result in Court?

You can absolutely challenge erroneous breathalyzer results in court. This is done in most cases through an expert witness.

If a call log or the maintenance log that are obtained from the Virginia Department of Forensic Science show a machine that is giving very different results to the same individual over multiple breath tests, then it can be argued, and evidence can be introduced by the expert witness, that the machine is malfunctioning.

If the machine is malfunctioning, then the evidence of the breath test can in fact be suppressed or in other words, kept out as evidence. Even if it is still admissible, the court may not give it enough weight to sustain a conviction.