A motorist stopped on police suspicion of drunk driving can easily feel intimidated and stressed. Not only are the flashing lights and encounter with authority unsettling; so, too, are the number and variety of tests that are often administered. These can include breath and blood testing, as well as field sobriety tests.

DUI stops and related alcohol tests are routinely challenged on various grounds (probable cause, false arrest, malicious prosecution, improper equipment and erroneous readings), with obviously varied results. Charges are upheld. Sometimes they are reduced or thrown out completely.

What is crystal clear, though, is that complications and uncertainties exist and are coming increasingly to light regarding the administering of alcohol-related tests and their results. Recently in Michigan, for example, the state's Supreme Court ruled that the presence of carxboxy - a metabolite resulting from the breakdown of THC, marijuana's active ingredient - can no longer be considered a controlled substance under state law. Prior to the ruling, a person with carboxy in his or her system could be prosecuted for drunk driving, even though not drunk.

A new challenge may come from acid reflux, which experts say can produce a false positive on a DUI breath test. According to Michigan DUI expert Mike Nichols, breath-testing equipment is supposed to measure alcohol coming from a person's lungs. A person with acid reflux regurgitates stomach contents into the mouth, which can contaminate a breath sample. Says Nichols: "If the instrument is measuring both, it is no different than standing on your scales at home with a 50 pound back of rocks and expecting the scale to measure your accurate body weight."

Nichols says that any test that is reading both mouth alcohol from a suspect's stomach as well as from that person's lung region can be reasonably questioned.

Related Resource: duiattorney.com "Acid reflux can make an innocent person look guilty of DUI" July 13, 2010