For a Maryland prosecutor to convict an individual charged with driving under the influence, he or she generally must prove impairment during the time of arrest. When a law enforcement official pulls you over, however, the portable device used for testing blood alcohol content may not always provide precise results. 

An arrest made based on an inaccurate BAC level could result in an individual facing a DUI charge, an offense that may include jail time and a fine. You have a right to contest the charge; a prosecutor may only convict when substantial evidence shows the court that you were actually impaired. 

Certain factors may cause a roadside breath test device to be inaccurate 

To request a motorist to submit to a breath test, a law enforcement official must have reasonable cause to believe that the individual was driving while impaired. When a driver has bloodshot eyes, fails a field sobriety test or shows confusion, an officer could decide to administer a breath test. The roadside testing device, however, may provide a BAC that is off by more than 40%, as reported by The New York Times. An incorrectly calibrated roadside device, for example, may provide a faulty result. 

Some device types detect an individual’s BAC level by relying on fuel cells that respond to alcohol in an individual’s breath. When an individual’s breath mixes with the fuel cells and generates an electrical current, the device interprets it as the amount of alcohol in the person’s system. Stronger currents indicate a higher BAC level. The currents, however, could respond to substances other than alcohol. The device may misinterpret traces of breath mints or gum that a motorist consumed or chewed prior to blowing into the machine. 

An effective defense may avoid a DUI conviction 

Motorists have a right to counter a DUI charge so that they may avoid a conviction. Under certain circumstances, individuals convicted of alleged DUI offenses may find their charges dismissed or deferred after meeting specific alternative sentence requirements set by the judge.