- September 26, 2018 |
- Category: DUI Testing
Testing blood alcohol content (BAC) based on breath samples has been a basic tool of the law enforcement community since the early 1940’s, when a scientist in Indiana developed a device known as the “drunkometer.” The drunkometer was soon adopted by police departments across the state of Indiana and utilized in DUI investigations. These breath testing devices were later refined and further developed. They are now a tool of every police department in the country. Drivers who fail the tests face criminal penalties for violating laws that prohibit driving with a prohibited blood alcohol content. These DUI laws are called “per se” statutes.
Per se DUI laws do not require the government to prove a driver was drunk, or even impaired by alcohol at the time he was driving. Rather, the government only has to prove the driver had a certain prohibited level of alcohol in their system, whether it impacted him or not. The government will generally utilize a breath test to determine blood alcohol content in Ohio DUI cases. Of all the tests used to measure blood alcohol content, by far, the easiest and most cost-effective is a breath test. However, it’s an indirect measurement and leaves the government’s case open to attack by a good DUI defense attorney.
The scientific principle underlying the approval of using a person’s breath to test for blood alcohol is called “Henry’s Law,” named for a chemist named William Henry, who came up with it in 1803. Henry’s Law predicts that when an unstable substance (such as alcohol) is dissolved in a certain solvent (such as blood), the concentration of the alcohol in the vapor over the substance (for example, your breath) will be equal to its concentration in the blood. However, it is important to note that Henry’s Law requires a closed system where there’s a continuous pressure and temperature. Experts aren’t so sure whether the human body meets the criteria for a closed system.
A person’s deep lung air is supposed to correctly reflect what is in the person’s blood. Thus, in theory, a breath test is as good as a blood test. The Ohio legislature and courts have decided that deep lung air tests are sufficiently reliable to be admissible in court. Unfortunately, the government should ascertain whether there are more reliable methods of analysis. While breath tests can reliably detect the presence of alcohol in the body, it is less clear that breath testing can provide an accurate measurement of the amount alcohol in the blood. The requirements of Henry’s Law, that being a closed system with constant pressure and temperature, probably don’t apply to the human lungs. Factors in blood-to-breath ratios have historically provided a fertile area for a seasoned DUI defense attorney. Scientific research, published in peer-reviewed journals, now shows that results from breath alcohol evaluation or breath testing may not be reliable for purposes of quantitative analysis.
