PHOENIX — Just because equipment used to measure blood-alcohol content occasionally malfunctions does not make the results of every test unreliable, the Arizona Supreme Court ruled Thursday.
In a case involving multiple defendants charged with aggravated drunken driving, the justices acknowledged that the equipment would occasionally fail to produce results. The justices said there also was evidence of mislabeling of vials and emails among staff members of the crime lab of the Scottsdale Police Department “expressing concerns about the instrument.”
Those problems were enough to get a trial judge, after a 17-day hearing, to throw out the results.
But Chief Justice Scott Bales, writing for the unanimous court, said everyone involved agrees the method of testing, a gas chromatograph, is generally presumed reliable. He said questions of whether a specific piece of equipment was properly used should be decided by a jury after hearing all the evidence.
Thursday’s ruling means the charges against the 11 defendants, all involving driving drunk while a license is suspended, revoked or otherwise restricted, will be reinstated and they will have to go to trial.
Bales said court rules generally require judges to “serve as gatekeepers,” assuring expert testimony, including lab results, are reliable and meaningful in helping a jury determine if the charges are true. That’s what permits a judge to rule certain evidence inadmissible.
But Bales said not every problem with equipment and methodology that is generally presumed reliable means that any data produced is unreliable and cannot be admitted into evidence. He said exclusion should occur only when the errors are “so serious as to render the results themselves unreliable.”
For example, Bales said, it might be proper to exclude test results if the lab staff omitted a step necessary to obtain valid results.
“But the fact that the instrument here sometimes failed to produce a reading does not itself imply that the results it did generate were inaccurate,” he wrote. And he said that while there were incidents of mislabeling, there was no evidence here that these defendants’ samples were misidentified.
“That is not to say that the malfunctions or the lab’s failure to resolve them are irrelevant,” Bales said. But he said it is up to the jury to consider the malfunctions and the lab staff’s related concerns in determining how much weight to give to the results produced.
