Individuals in borderline driving under the influence (DUI) cases in New Mexico now have a chance of proving their innocence after an Appeals Court decision released on June 1.

The case involved a Lincoln County man named John Day who was pulled over because his license plate was not illuminated. His driving did not exhibit any signs of impairment. When the police officer noticed an open container of beer in the car, however, he performed a field test and arrested Day for drunk driving. A breath test conducted 66 minutes after the stop showed Day was right at the .08 blood alcohol limit. Day later was convicted in a Lincoln County District Court based on this evidence.

Because the blood alcohol reading rises over time as alcohol is absorbed into the bloodstream, Day's reading may not have accurately reflected his blood alcohol level at the time he was driving, according to Doctor Edward Reyes, a pharmacologist who testified for the defense. The appeals court ruled that it was improper for the state to ignore this evidence.

"We hold that absent scientific evidence of the alcohol absorption and elimination processes tied to facts that must be considered in scientifically evaluating the alcohol absorption rate of a particular driver, the jury could not have rationally inferred that defendant had a .08 alcohol content at the time of driving," Judge Jonathan A. Sutin wrote for the court in a 3-0 decision.

The judges suggested that a "retrograde extrapolation" should have been done to estimate Day's intoxication level at the time he was driving based on the time of alcohol consumption and other relevant factors. The judges suggested that the law may need to be changed to ensure a constant stream of convictions. "The problem of proof also raises the question of whether a new statute is needed to overcome the difficulty of proof," Sutin wrote.

The complete text of the ruling is available in a 137k PDF file at the source link below.