The devices gather just one of several pieces of evidence in most drunken driving cases.
For the third time in less than a year, hopes of exoneration by hundreds of drunken driving suspects were raised when a district attorney announced widespread problems with hand-held devices police use during field sobriety tests.
But just like the previous two dustups in Santa Clara and Ventura counties, the San Francisco review of about 1,000 DUI cases was expected to lead to few dismissals.
That's because results from the devices were just one of several pieces of evidences collected in the overwhelming majority of drunken driving cases.
Still, officials and lawyers say there could be some dismissals because a few cases featured the so-called PAS testing as the only valuable piece of evidence.
The latest flap over the devices began Monday when San Francisco District Attorney George Gascon announced his office would review cases involving the Alco Sensor IV, manufactured by St. Louis-based Intoximeters Inc. The company didn't return a phone call Wednesday seeking comment.
The announcement was prompted by the disclosure that the San Francisco Police Department was failing to properly test the devices. The manufacturer recommends that the devices be tested every 10 days or after 150 uses. San Francisco Public Defender Jeff Adachi said his office noticed that police maintenance records showed the same reading in every test of the devices.
"It's a mathematical impossibility to consistently have the same results for sample testing and the actual reading," Adachi said.
Police Chief Greg Suhr told The Associated Press he's unhappy with his department's handling of the devices that his officers stopped using in February as the department revamps its policy on maintaining the PAS. He also reported the problem to the San Francisco Police Commission two weeks ago.
He stressed, however, that the devices are only one of five factors typically used to establish probable cause for an arrest.
"It's reference tool," he said.
He said drunken driving arrests can still be made based on other factors, without results from the device. Officers also arrest suspects based on how they were driving, how they appeared when pulled over and whether they failed other field tests such as walking a straight line or reciting the alphabet backward. All of that evidence can be used against a DUI suspect in court.
Suhr also said DUI suspects are still required to submit to a more conclusive blood, breath or urine test once they are taken to jail. It's that more definitive test that is used as courtroom evidence on drunkenness.
"The machines were just a brick in the wall," Suhr said. "The foundations of the arrests are still solid. Regardless of what happens in the field, you still have to give blood, breath or urine samples."
The San Francisco district attorney said Monday that 98 percent of all cases being reviewed include this additional evidence that makes officials confident that few cases will be dismissed because of problems with the field-sobriety devices.
Last year, Santa Clara and Ventura counties discovered problems with the next-generation PAS, known as Alco Sensor Vs.
After a dramatic announcement that hundreds of cases would be reviewed, only a handful in each county were tossed out.
Santa Clara deputy district attorney James Gibbons-Shapiro said his office reviewed 930 DUI cases last year involving the PAS in question. He said no guilty pleas were reversed and three or four pending cases were dropped because of problems with the devices.
The two agencies using the devices have returned to using the Alco Sensor IV — the model at issue in San Francisco — with no problems while the manufacturer fixes the problems with the next-generation PAS, he said.
"For the vast majority of DUI cases, the PAS are usually a small part of the puzzle," he said.
The Ventura County district attorney didn't return a phone call.
Overall, about 80 percent of the roughly 200,000 annual drunken driving arrests a year in California result in a DUI conviction.