What Is The PBT, or Preliminary Breath Test?

The PBT is the preliminary breath test. It’s also referred to as a portable breath test. It is a small machine that the officer can carry in his or her vehicle that allows them to get a general reading of a suspect’s blood alcohol content. The suspect blows into it, and it registers a number.

What Is The Difference between The PBT And The Breath Test At The Station?

The big difference between the PBT and the breathalyzer at the station is that the results from the station breathalyzer are what will be used to revoke somebody’s license, and the result of that test can be used in court to prove intoxication. The machine used in Oklahoma is the Intoxilyzer 8000.

Preliminary Breath Test

The PBT is not considered scientifically accurate enough to use for the purpose of license revocation. There are numerous models of PBT, and there is no standardization. In contrast, the model of the breathalyzer machine used in Oklahoma is the same all over the state. There is a standardized procedure for administering a breath test on the Intoxilyzer, but there is no standard method of administering a PBT.

Is The PBT Voluntary Or Mandatory In Oklahoma?

Submitting to a PBT is completely voluntary in Oklahoma. It has not been used very much here until recently. Oklahoma officers are increasingly using the PBT. It’s supposed to be used as a confirmatory tool after the field sobriety tests are done. The officer is supposed to administer the SFSTs then confirm that the individual is impaired on alcohol by using the PBT. If a person does poorly on the SFSTs yet registers a very low, or zero, value for alcohol content on the PBT, then the officer is going to believe that the suspect was impaired on a substance other than alcohol. At that point, the officer would administer other field sobriety tests, attempt to have a Drug Recognition Expert Evaluate the suspect, and/or get a blood test.

Sometimes, the officer will administer the PBT prior to administering the field sobriety tests. This is incorrect. The reason is that if the officer sees the reading on the PBT, then it will cloud their evaluation of the person’s performance on the field sobriety tests. The officer will then analyze the performance of the SFSTs based on a belief that the suspect is impaired at a certain level.

Officers are sometimes tricky when getting people to blow into a PBT. They will not ask somebody if they would like to blow into the PBT. They will get the machine set up, put the mouthpiece in it, stick it in somebody’s face, and say, “Here, blow into this.” That makes it seem like the PBT is not optional, but it is. You do not have to blow into a PBT in Oklahoma.

What Happens If Someone Refuses To Blow Into The PBT?

If somebody refuses the PBT, then the officer will have to use other observations to determine whether probable cause exists to arrest an individual for impaired driving. The officer will have to take into account things such as their observation of the suspect’s driving, SFST performance, an odor of alcohol emanating from the individual, what the individual said, whether the individual was unsteady on their feet, and other indicators of intoxication. The result from the PBT is just one of many potential indicators of intoxication. There is no criminal or driver’s license penalty for refusing to blow into a PBT.

What Factors Impact The Reliability Of A PBT Result?

There are numerous things that can result in a false PBT result. Residual mouth alcohol and breath contaminants can cause a PBT result to be higher than actual blood alcohol content. It takes approximately 15 minutes for residual alcohol to be eliminated from the mouth. Therefore, the officer is supposed to ensure that the subject has not consumed any alcohol for 15 minutes prior to using the PBT. An officer rarely does this. Other substances can skew the results high on a PBT. These include chloroform, acetone, and cigarette smoke.

Two factors can cause a PBT result to be lower than the actual blood alcohol content. These are breath sample cooling and breath sample composition. If the captured breath sample is allowed to cool before it’s analyzed, some of the alcohol vapor in the breath may turn to liquid and precipitate out of the sample. If that happens, then a subsequent analysis of the sample will yield a low BAC. Breath composition is the mixture of the tidal breath and alveolar breath. Tidal breath is breath from the upper part of the lungs and the mouth. Alveolar breath is deep lung breath. Breath testing should be conducted on a sample of alveolar breath. This is obtained by having the suspect blow into the PBT instrument until all air is expelled from the lungs.

A factor that can cause either a low or high PBT result is radio frequency interference. It can also prevent a breath test device from producing any result. Most officers have a radio that’s very close to their body, which can be very close to the PBT when the officer is asking a suspect to blow into it.

There are accuracy limitations on PBTs. They are not calibrated to the same standards as the breath test machine at the station.

Is The Result Of The Preliminary Breath Test Admissible In Court?

The fact that a PBT was administered is admissible in court. The fact that a PBT gave the officer probable cause to make a DUI arrest is also admissible in court. What is not admissible in court is the actual numerical output from the PBT. For example, if somebody blows a 0.10 on the PBT, that 0.10 number can’t be entered into evidence. This is because the PBT is not considered reliable enough to use in the criminal prosecution against somebody. Its use is not standardized, and it’s not calibrated to the degree that the Intoxilyzer is.

Source: NHTSA’s 2015 DWI Detection and Standardized Field Sobriety Testing student manual

For more information on the Preliminary Breath Test, PBT, In Oklahoma, call (405) 633-3420 to speak with an attorney.