An investigation in the San Francisco Police Department discovered that breathalyzers were not being tested properly, resulting in the possible overturn of thousands of DUIs.

But in Columbia, police rely on devices out in the field solely as a sobriety test, indicating that nothing of that nature could happen here, MU Police Department spokesman Brian Weimer said.

“That couldn’t happen here because the devices out in the field here are not used for that purpose,” he said. “You would still have to go to the station and blow into a breath instrument.”

Police in Columbia use breathalyzers as well as tests including the one-legged stand or the walk and turn. Although two of these methods are under the individual’s control, the breathalyzer is simply a preliminary breath test that police rely on to perform accurately.

An investigation in the San Francisco Police Department revealed that its police officers had not been conducting tests on their preliminary alcohol screening devices in the past six years. Additionally, the SFPD used testing solution that expired in 2010, meaning that DUI cases dating back to 2006 will now have to be reviewed.

Unlike with the SFPD, Columbia’s breathalyzer cannot be used in court as evidence as to whether or not someone will be charged for a DWI. It can, however, lead to an arrest if the officer determines the driver is incapable of operating a car.

Boone County saw 276 DWI incidents in 2011.

Two different types of breathalyzers are used, said Deputy Nikki Antimi of the Boone County Sheriffs Department. The portable breath test, which is used in the field, is not evidentiary in court, but it can be used to detect impairment in a driver and give probable cause for an arrest. The evidentiary-based types use the Alco-Sensor 4, carried in the vehicles designated for DWI enforcement, and the BAC Data Master, an instrument stationed inside of the jail.

Both the Alco-Sensor 4 and the BAC Data Master have had validation studies for proven accuracy, along with scientific studies, CPD Sgt. Curtis Perkins said.

Missouri breathalyzers must be tested every 35 days to make sure they are operating accurately. Other factors are also examined when observing the machine, such as radio frequency interference, temperature and display.

Local law enforcement said they understand that field machines aren’t always accurate, which is why they don’t rely solely on them, unlike with SFPD’s incident, Perkins said.

Considering they might pick up on things like alcohol from a person’s mouthwash, options besides using field breath tests are available, he said. Blood tests are among the most reliable forms of alcohol testing, but are also inconvenient because results are often delayed, Perkins said.

But with the SFPD, investigators are seeking out other results, in an attempt to determine how to handle the overturn of possibly thousands of cases.