SAN FRANCISCO (AP) — Hundreds of San Francisco drunken driving cases could be tossed because of possible mishandling of field sobriety devices by police officers.

Public Defender Jeff Adachi, whose office is working with prosecutors to identify DUI cases in jeopardy, said Monday that up to 1,000 convictions could be thrown out. Adachi said his office is reviewing cases dating back to 2006.

Adachi said the review was focused on the hand-held device police use to test motorists immediately after traffic stops. Adachi said the review was prompted after several attorneys in his office noticed that police maintenance records showed the same reading in every test of every preliminary alcohol screening device, which require accuracy checks every 10 days or after 150 tests.

"It's a mathematical impossibility to consistently have the same results for sample testing and the actual reading," Adachi said.

Adachi said that his office has set up a special number 415-553-1081 for those represented by a San Francisco public defender convicted of a DUI to call. Adachi urged others convicted of DUIs to contact their private counsel.

San Francisco District Attorney George Gascon has suspended use of the device in pending cases. Gascon said prosecutors are barred from using the results of the devices until the police department changes its testing policy. Gascon said his office is also reviewing closed DUI cases that relied on the devices.

"We are in the process of identifying cases that could be affected," Gascon said. "Until the review is done we don't know the number of cases that could be affected."

Gascon's office noted that the devices in question are the Alco Sensor IVs and not the next generation Alco Sensor V, some of which were returned to the manufacturer last year by several California agencies that reported faulty readings. Both sensors are manufactured by the St. Louis-based Intoximeter Inc., which said it fixed the cause of the Alco Sensor V's problems.