Criminal Defense Lawyer | DWI, Drug, Theft & Assault Charges

By Collin County Criminal Lawyer Jeremy Rosenthal

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Breath Test Devices in General

In DWI prosecution and defense there are several occasions where a person may give an optional or sometimes mandatory breath specimen.  Obviously at the arrest, a person is given the opportunity to provide a breath specimen.  After the arrest either while on bond or if after conviction — people are often required to submit to testing to start their car or carry a device which tests them periodically.

Only one machine in Texas is currently used and admissible to show a blood alcohol concentration (BAC).  This is the Intoxylizer 5000 which is almost always located at the police station in a special room where DWI arrestees are taken and read statutory warnings.  Any other testing device used in Texas is currently not considered scientifically accurate enough to do anything other than indicate the mere presence of alcohol in one’s system — yet those devices still report a numerical reading.

Other testing devices come in forms such as interlock ignition device (deep lung device or “DLD” for short), portable breath test devices carried by police officers for quick field tests (“PBT”) and portable devices carried around by someone on bond or probation and attached through a smart-phone like connection which requires breath samples throughout the day and reports the results to a probation officer.

Portable Breath Test Devices

Today’s discussion isn’t about the intoxylizer machine but about the other three devices which for today’s purposes I’ll just refer to as PBT technology.  This is because the ladder three devices discussed above operate on what is known as “fuel cell” technology.  Fuel cell technology is highly complex but what is important is (as companies who make and sell services for these devices will readily admit) is these devices are simply not very accurate and extremely susceptible to false-positives.

Common Flaws of PBT Devices

For starters, at least one company claims the accuracy of their device to have a 0.05 margin of error.  In other words, someone who blows a 0.08 might be as high as a 0.13 or as low as a 0.03.  This is the difference between being highly intoxicated and having one glass of wine for some.

The company asks people to wait at least 20 minutes to blow after eating, drinking, or smoking.  The company admits cologne, perfume, hand sanitizer, and toothpaste can result in false positives.  Users are warned not to wear sunglasses or take the test any place where large amounts of alcohol are being consumed.

Courts are admonished by the providing companies the company itself “does not warrant the veracity of readings as evidence.”

The Biggest Problem With Portable Breath Test Devices

The biggest problem isn’t the inaccuracy or fallibility of the testing.  The companies providing these services are honest in telling us what their devices can and can’t do.  The problem is probation officers and courts who treat these device readings as the gospel and mock victims of the short-comings of the technology.

Many probation officers use deliberate and careful discretion in evaluating the results of some of these devices — but unfortunately — some do not.

One thing you learn quickly as a criminal defense attorney is how almost impossible it is to prove a negative.  Failing a PBT test puts you in this position with some evaluators who don’t believe these machines are fallible.  There is virtually no explanation you can give in your defense a probation officer can’t accuse you (or someone testifying on your behalf) of lying about.

What you can do is show how fallible the device might be.  But this assumes the listener has an open mind.  This is the biggest problem with portable breath test devices.

Users are instructed to re-attempt a sample after 10, 20 or 30 minutes to show the first result was a false positive — or if the machine is completely on the fritz — to go to a 3rd party testing agency to prove you haven’t been drinking… Here’s hoping your not in a job interview, the Mojave Desert, or on an airplane!

In Closing

One last admonition from a service provider instructs a person in the event of repeated false positives to have themselves tested by a third party — I’m guessing like an independent test lab.  If that doesn’t get done, good luck telling your probation officer you were in the middle of a job interview, important meeting, or driving through the dessert.  They can see right through those excuses.

*Jeremy Rosenthal is Board Certified in Criminal Law by the Texas Board of Legal Specialization and licensed by the Supreme Court of Texas. Nothing in this article is intended to be legal advice.  For legal advice about any other situation, you should contact an attorney directly.