Breathalyzer Lies
One of the main tools police use in proving their case is a hand-held breath-testing device often called a “breathalyzer” and also known as a Preliminary Breath Test or Roadside Breath Test. After the badge and the gun, this is one of the most-recognized police devices. But few people understand how many half-truths and outright lies surround its use.
Several models of Preliminary Breath Test (PBT) are used in Virginia. All use an electro-chemical fuel cell that passes a current through two platinum electrodes, one of which will have oxidized any alcohol in your breath. Comparing the difference in the current results in a number that is supposed to reflect your Breath-Alcohol Concentration (BAC).
The first (and worst) lie that many people are told about this device by the police is “this test can’t be used against you in court.” What a surprise, then, that the test is mentioned in every DUI trial. In fact, it would be more legally accurate for the officer to say “this test can’t be used against you in a prosecution.” This is what the law says. But even that is misleading. According to the Virginia Supreme Court, not every aspect of your trial is a “prosecution”. Funny, but when you’re on trial and you might go to jail, it all feels a lot like a prosecution. The PBT can and will be used at trial to show that the officer had the authority to arrest you.
Manufacturers and law enforcement like to discuss the accuracy of these devices, but they can produce a host of “false positives” and “false negatives”, meaning that they can indicate sober people are drunk and vice-versa.
The computer inside the PBT multiplies the amount of alcohol detected by 2100. This is because it is assumed that the average individual has a ratio of 2100 units of alcohol in his blood for every one in his breath. This is known as the “partition ratio”. In fact, the true amount varies widely from individual to individual, from as low as 900:1 to as high as 3500:1. If your partition ratio isn’t exactly 2100:1, the reading will be falsely high or low. Thus a person with a measured BAC of 0.08 might actually have a true BAC anywhere from 0.034 to 0.133. And that’s just plain unfair.
Manufacturers also claim the PBT is “specific for alcohol”. However, the human body produces alcohol naturally. Eat a slice of white bread, chew it slowly, taking a minute or so. Then blow into a PBT. You will have alcohol on your breath. As much as a 0.04. It also works with soy sauce and a vast variety of other foods.
Manufacturers also claim that is necessary to blow hard into the PBT to get an accurate result. They claim that something they call “deep lung air” gives the most accurate results. In fact, blowing harder simply produces a higher result. “The more you blow, the higher you go,” is a phrase often heard in breath testing.
Finally, there is an assumption that your breath has come solely from your lungs. But individuals who suffer from Gastroesophageal reflux disease (GERD) (also known as acid reflux) and have any alcohol in their stomachs may be emitting that alcohol directly into their throats, where it coats the mucus membranes of the mouth and sinuses and can give a falsely high reading as much as 150% of the true BAC. Thus, a person suffering from GERD who has a measured BAC of 0.10 might actually have a BAC as low as 0.66. Even assuming a partition ratio of exactly 2100:1.
Remember, this test and all the other roadside tests are voluntary. You do not have to take it and you should not take it. Ever.