State Sen. Bill Diamond, D-Cumberland County, is questioning the effectiveness a proposed bill, sponsored by a fellow Democrat, would have on drunk drivers.

State Sen. Lynn Bromley, a Democrat from South Portland, is behind a bill that calls for the installation of ignition locking devices in cars owned by convicted drunk drivers.

The devices, often a phone-shaped box on a spiral cord, are installed into the dashboard and the vehicle cannot be started until the driver blows into it, allowing the device to estimate the person’s blood alcohol level.

If the “ignition interlock” detects a blood alcohol level that is too high, the vehicle will not start.

The cost of the devices would be paid for by the offenders, said Diamond.

Diamond is co-chairman of the Criminal Justice and Public Safety Committee, where the bill is headed.

“I’m not opposed. I’m just skeptical,” said Diamond.

Diamond said he investigated ignition interlock devices in the 1990s when he was secretary of state and found them too unreliable. Another person could blow into the device or the offender could use another car, he said.

The technology has probably improved over the last decade, Diamond said, but with the number of technical problems they posed in the past he does not know if it would have any impact on repeat drunk drivers.

“The technology has gotten quite good.” said Bromley. She said in the past the devices had problems detecting alcohol but that has been fixed.

She compared individuals that would help a drunken driver fool an ignition interlock device to the get-away driver for a bank robbery.

“It’s like handing someone a loaded gun,” she said.

Bromley would like to see family members of convicted drunk drivers be given informed consent forms to make sure they understand they will be prosecuted if they are caught lending out a vehicle or defeating a device.

Recent ignition interlock devices have a “rolling checks” system, according to Bromley. At random intervals during a drive the device will beep and require additional tests. Upon failure the automobile would not be stopped, but the incident would be recorded in an electronic log.