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The Tyndall Effect – How an Airbag Can Effect Your Breath Test in a DUI

Over the years, our DUI defense lawyers in Charleston have handled many cases involving auto accidents. Under South Carolina law, Section 56-6-6170, “no police officer in investigating a traffic accident shall necessarily deem the fact that an accident has occurred as giving rise to the presumption that a violation of the law has occurred.” Yet, if you’re involved in an auto accident, and the police suspect that you’ve consumed ANY amount of alcohol, chances are you’ll be arrested for DUI. This article examines the reasons why an accident can actually make it HARDER for the prosecution to show that you’re guilty of DUI.

Physical and Mental Abilities of an Accident Victim

A driver who’s been in an accident will seem physically and mentally impaired due to the trauma of the collision. While many people may be shaken up due to the accident, others will experience shock. Doctors define shock as a “circulatory collapse” that occurs when blood pressure dips too low to maintain an adequate supply of blood to the body’s tissues. Symptoms include cold and sweaty skin, weak and rapid pulse, irregular breathing, dry mouth, and dilated pupils. Whether the driver is simply shaken up or in shock, they will exhibit signs of mental confusion and physical impairment as a result of the accident. Under these circumstances, it is no wonder that drivers in accidents mirror many of the symptoms of being under the influence of alcohol and will likely fail any field sobriety tests. Under these circumstances, it is difficult for any prosecutor to show that the driver’s physical or mental impairment was alcohol-related as opposed to the natural consequences of being involved in a vehicular collision.

Air Bags & the Tyndall Effect On Breath Tests

Any person who’s experienced an airbag will tell you that they get an awful taste in their mouths and sometimes it is difficult to breathe. When an airbag inflates, a puff of “smoke” can be seen coming from the steering column or side airbags. This “smoke” is a result of cornstarch or talcum powder that was commonly used to line the inside of the airbag to aid in deployment. Although newer airbag fabrics are sufficiently “slippery” that additional powder lubricants aren’t necessary, most side airbags are still lubricated with talcum powder. In any event, the driver typically inhales microscopic particles of the powder lubricant that they cough up for hours.

South Carolina’s breath test machine, the DMT Datamaster, uses infrared lasers to measure how the infrared light is obscured by the presence of alcohol particles in your breath. If you take to a breath test after an airbag has deployed in an accident, the Tyndall effect, also known as Tyndall scattering, can cause a false high reading.

The Tyndall effect happens when light is scattering by particles. When you blow into the Datamaster, you will also blow some of the microscopic particles of lubricant powder into the sample chamber at testing. The powder acts like little mirrors deflecting and diffusing the infrared laser beam inside the Datamaster (the Tyndall Effect). The diffraction and diffusion of the infrared light cause a false high result in the breath test. In other words, if a person has been exposed to an airbag deflation before breath testing, then the accuracy of the breath test results is highly questionable.

DUI Defense Lawyers in Charleston

If you’ve been charged with DUI or DUAC in Charleston or the surrounding areas should contact the lawyers at Futeral & Nelson and schedule a free consultation. We know how to defend DUI’s or traffic tickets and we’ll fight to keep you on the road and to keep your job.

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