Studies show portable breath test readings are unreliable

Illinois law officers use portable breath test devices to find out whether a driver is intoxicated. Studies show that these devices give inaccurate and unreliable results.

When people decide to drink and drive, they run the risk of being charged with a DUI in Illinois. However, motorists who are not driving while intoxicated run the risk of getting arrested for a DUI as well. Studies show that portable breath test devices, also known as PBTs, do not always provide accurate readings. In fact, the State University of New York at Potsdam showed that approximately 23 percent of people who are tested with roadside breath test devices will have inflated blood alcohol content level readings. In some cases, these erroneous results could lead to a wrongful DUI arrest and possible charges that could have a negative effect on people's lives.

Comparing blood alcohol tests to breath test results

One way that law officers tell whether a driver has a BAC that is over the legal limit of 0.08 percent is to measure the amount of alcohol that is present in his or her blood. It can be difficult to perform a blood test on the side of the road, and so law enforcement officers use portable breath test devices to determine a driver's BAC level. Breath tests calculate the driver's blood alcohol concentration indirectly, by measuring how much alcohol is present in the motorist's exhaled air content. Research shows that portable breath test readings can vary by at least 15 percent from the results obtained from a blood test.

Factors that skew PBT readings

What makes breath test readings so unreliable? There are a number of environmental and physiological factors that can make PBTs ineffective. According to studies performed by the State University of New York at Potsdam, these include:

  • Electrical interference coming from cellphones and officers' radios
  • Pollutants in the environment, such as cigarette smoke, dirt and gasoline fumes
  • Any residual substances in the subject's mouth, such as vomit, blood or food
  • Any type of fumes the driver has been exposed to, such as paint thinners, paints and cleaners
  • Whether the officer is using the PBT properly

According to Illinois administrative code, portable breath test devices must be calibrated and checked for accuracy every 62 days.

In addition, portable breath test devices have been found to measure more than just the amount of ethyl alcohol contained in a driver's breath sample. The machines also pick up methyl alcohol groups, which are similar in structure to ethyl alcohol but are found in other substances-including human saliva.

Defending your rights

If you are facing criminal DUI charges in Illinois, you may want to consider speaking to a knowledgeable attorney regarding your legal rights. A DUI can make it extremely difficult to find employment in certain industries, obtain a professional license or receive certain types of funding. A lawyer may be helpful in answering your questions and helping you through the legal process.