Dozens of police departments are installing video cameras in patrol cars that resemble the "black box" recording devices in airplane cockpits, the manufacturer says.

About 50 police departments, including several in Michigan, have bought the $7,300 video units, and mall security and armored car companies are interested, according to CrimTech Corp. of Auburn Hills, Mich."We're looking at every police car having it within four years," said company President John Squicciarini. "That's over a $2 billion market in the United States alone."

Among those looking at the system is the Los Angeles Police Department, which will test a unit for 90 days, Squicciarini said.

Los Angeles police have been under fire since the March 3 police beating of an unarmed motorist, Rodney King.

King, who's black, was repeatedly kicked, clubbed and shocked with an electronic stun gun by white officers in an incident videotaped by a resident of a nearby apartment.

Los Angeles Police Lt. Paul Enox said the decision to test the system was unrelated to the King incident.

Another department spokesman, Larry Fetters, said the equipment is likely to be popular with civil liberties groups.

"Clearly it would document the behavior of the officer," he said.

Paul Denenfeld, legal director of Michigan's American Civil Liberties Union chapter, welcomed the technology - as long as the cameras are "kept on at all times."

"One of the potential benefits of having video cameras is exactly to prevent what happened in L.A. from happening anywhere else," Denenfeld said.

Filming citizens without their knowledge can make privacy rights an issue, but no one has yet raised it, Denenfeld said.

The system has a 2-inch-square camera mounted between a patrol car's mirror and windshield, linked to a recorder in the trunk. Like an airplane's flight recorder, it ties in to the officers' body microphones, the car's radar and other systems.

The video picture indicates the date, time, police department, car number, officers' numbers, speed of the patrol car, speed of other cars tracked by the radar unit, and whether lights or siren are in use.

"It allows the officer to stop, rewind and review," Squicciarini said. "He can show the violator what he was doing, that he was weaving in traffic or whatever."

The Troy Police Department is testing a unit in hopes that tapes of weaving vehicles and drivers faltering in field sobriety tests will cut down contested drunken driving cases and keep police out of court, Lt. Bill Tullock said.

Squicciarini also said the system is tamper-proof because a new recording begins where the tape was stopped.

The tapes could be offered as evidence in a court of law to counter false damage suits against police, Squicciarini said.

If would-be litigants see that the tapes don't back their accounts, Squicciarini said, they may drop their cases.

"It's ultimately going to turn into the vehicle's black box," he said.

CrimTech has four former law enforcement officers among its 15 employees.

Squicciarini wouldn't reveal the sales of the 2-year-old privately held company, but said he expects annual revenues to reach $5 million to $10 million within 12 months.