Do you want to trick a breathing machine into a low test result? Or do you make sure you’re not causing a false high reading? It’s not that difficult, says a San Diego DUI law firm and attorneys – just control your breathing.

The simple fact is, these DUI guilty or innocent breathing machines aren’t exactly the trustworthy devices law enforcement would have us believe. There are dozens of factors that can cause false test results. An example of this lack of reliability is the fact that results will vary depending on the breathing pattern of the person being tested. This has been confirmed in several scientific studies.

In one, for example, a group of men drank moderate doses of alcohol and then had their blood alcohol levels measured using a gas chromatographic analysis of their breath. Then the breathing techniques were varied. The results indicated that holding your breath for 30 seconds before exhaling increased blood alcohol level by 15.7%. Hyperventilation for 20 seconds immediately before breath tests, on the other hand, lowered the level by 10.6%. Keeping the mouth closed for five minutes and using shallow nasal breathing resulted in an increase in blood alcohol level by 7.3%, and the test after a slow exhale of 20 seconds increased the levels by 2%. (“How Breathing Techniques Can Influence Breath Alcohol Test Results”, 22 (4) Medical Science and Law 275.)

Dr. Michael Hlastala, professor of physiology, biophysics, and medicine at the University of Washington, went further and concluded:

“By far the most overlooked error in breathalyzer tests is the breathing pattern … Alcohol concentration changes considerably during breathing … The first part of the breath, after ruling out dead space , has an alcohol concentration much lower than the equivalent BAC (blood alcohol concentration) Whereas, the last part of the breath has a much higher alcohol concentration than the equivalent BAC The last part of the breath can be more than 50 % above the alcohol level … Therefore, a breath meter reading of 0.14% taken from the last part of the breath may indicate that the blood level is only 0.09%. ” 9 (6) Champion 16 (1985).

Many cops know. They also know that if the machine contradicts their judgment that the person they arrested is drunk, they won’t look good. So when the arrested person is told to blow into the mouthpiece of the machine, they will yell at him: “Keep breathing! Breathe harder! Louder!” As Professor Hlastala has discovered, this ensures that the breath captured by the machine will come from the bottom of the lungs, near the alveolar bags, which will be the richest in alcohol. With the higher alcohol concentration, the machine will give a higher, but inaccurate reading.