Because of an oversight earlier this year, Long Beach police officers were allowed to keep using a malfunctioning DUI screening device for more than a month after a technician determined it was unreliable, according to the department.

The device, which measures blood-alcohol levels by testing someone’s breath, was used twice in roadside investigations after it should have been decommissioned, Long Beach police officials said.

In one case, a woman was arrested and later pleaded guilty to drunk driving. In the second instance, officers cleared a Long Beach councilwoman of drunk driving based partially on the device’s measurement.

Police said they don’t believe either case would’ve turned out differently if the screening device were functioning properly.

But the mistake has prompted Long Beach police to make some changes, according to the department.

“It was just simply that, a mistake,” Long Beach Police Deputy Chief Rich Conant said. “And based on that mistake, some issues in our process were identified, and we’ve made corrective actions toward that. So we don’t expect to see that again.”

Police discovered the faulty screening device was still being used only after a high-profile incident on June 3 when officers used it to test Long Beach Councilwoman Jeannine Pearce, who was found pulled over on the side of the 710 Freeway in the middle of the night.

Pearce blew a .06 during the breath test and showed “mild impairment” during a roadside sobriety test, according to a description of the incident from the Los Angeles County District Attorney’s office.

Pearce’s former chief of staff, Devin Cotter, was also in the car with Pearce that night and accused her of domestic violence, but officers at the scene ultimately decided there wasn’t enough evidence to arrest her, according to authorities.

Prosecutors later declined to file any charges against Pearce, saying she and Cotter both gave inconsistent statements. They also concluded Pearce may have shoved Cotter to the ground in self defense.

Prosecutors still have an open public integrity investigation that involves Cotter and Pearce, according to authorities.

Shortly after the June 3 dust-up, Long Beach police started getting complaints alleging officers gave Pearce VIP treatment.

Police said they opened an internal investigation that cleared officers of those allegations, but, within a week of the probe starting, investigators discovered that the malfunctioning DUI device had been used to test Pearce.

The screening device was deemed unusable in early May, but it was left in a central storage area where officers could pick it up without realizing it was malfunctioning, according to Conant.

He said police yanked the device from circulation as soon as they found out, which was before it could be used in any more cases.

From now on, any time a similar screening device is taken out of service, police will put a piece of tape on it, sealing it closed and signaling to officers that it should not be used, Conant said.

Police said the device started malfunctioning in early May when it displayed an error message about a bad fuel cell.

But after clearing up the error, technicians weren’t able to get a proper baseline reading, according to Conant.

“The device itself has to have an air blank go through to bring it back to a baseline level, and it was not properly doing that, but we don’t know why that was, so we decided to remove it from service,” he said.

It’s unclear if the malfunction meant the device’s reading were inaccurate or not.

Greg Gossage, who oversees the Long Beach Police Department’s crime lab, said that when he tested the device again in August and September, it was registering alcohol amounts correctly.

Long Beach has been using these tools, known as Preliminary Alcohol Screening (PAS) devices in police parlance, since 2003, according to Conant.

Someone pulled over on suspicion of drunk driving will blow into the handheld device, which produces a measurement of their blood-alcohol content for the officer. They’re often called Breathalyzers, which is a brand name.

Officers use the PAS devices only to determine if there’s enough evidence to arrest a suspect and take him or her to a police station for more accurate blood-alcohol tests, according to Conant.

Because of this, nobody could be convicted of a DUI on a malfunctioning PAS test alone, Conant said.

But a faulty device can create headaches for a prosecutor if police don’t have other justification to back up their arrest, according to experts.

“Where this becomes problematic is where officers rely almost exclusively on the PAS device and its readings to establish probable cause,” said Jim Bueermann, a retired police chief from Redlands who is now president of a law enforcement research nonprofit called the Police Foundation.

If a suspected DUI driver was arrested based only on a reading of .08 or above, the arrest could be invalidated if the test was later determined to be faulty, according to Bueermann.

Conant said this did not happen in Long Beach.

Long Beach officers are trained to use the PAS device as just a single piece of evidence to be used in conjunction with traditional field sobriety tests to decide whether someone’s impaired, according to Conant.

“It’s not a stand-alone device,” he said. “That’s not how we use it.”

Long Beach police said they have about 30 other PAS devices all in proper working condition. No other malfunctioning devices were accidentally used, according to Conant.

Technicians test them every 30 days for accuracy, which is in line with the manufacturer’s guidelines, Conant said.

The Los Angeles Sheriff’s Department tests its PAS devices every 10 days or after they have been used to test 150 subjects, according to spokeswoman Nicole Nishida.

There’s no law that mandates how often police have to test PAS devices for accuracy if they’re primarily used to build probable cause for an arrest, according to experts.

By contrast, state law requires that any blood-alcohol test used in court as scientific evidence must be calibrated every 10 days.

Readings from PAS devices that don’t meet those standards can still be presented to a jury, but they doesn’t carry as much weight as the more finely tuned measurements.

Beyond the stop involving the councilwoman, officers Long Beach’s faulty PAS device was used only one other time, according to police.

On June 2, an officer pulled over a 22-year-old Carson woman, according to authorities.

Police said the PAS device registered her blood-alcohol level at .15 when she blew into it at the scene.

As is standard procedure, police did follow-up tests of her blood-alcohol levels about 40 minutes later once she was in custody at a station where she registered a .12 and then a .11, according to Conant.

The woman has since pleaded guilty.

Her lawyer said last week that he didn’t know about the faulty test until a reporter brought it to his attention, but even if he had, the outcome of the case likely would have been the same.

“In her particular case, it would not have made a difference,” attorney Justin Lo said.