BOSTON -- When you say "black box", the crash data recorder retrieved after airline disasters immediately comes to mind.

RESOURCES Vehicles That May Have A CDR

So, it may come as a surprise to learn that millions of cars and trucks are also equipped with a similar device imbedded deep in the airbag module.

NewsCenter 5's Jorge Quiroga said that while these "black boxes" were designed to monitor vehicle safety, criminal charges against a Beverly, Mass., woman are now testing another use for this device.

With 5 prior sur-chargeable accidents on her record, few will deny that police should have been watching 33-year-old Michelle Zimmerman closely.

But what has everyone's attention is her sixth accident, and the "crash-data" obtained from a small 4-inch square silver box, when no one was watching.

In early January, Zimmerman was driving her GMC Yukon when it slid into a tree on Argilla Road in Ipswich, Mass. Her passenger, Kenneth Carlson, was killed on impact.

Last month, Zimmerman was charged with vehicular homicide by negligence and speeding.

"This will be a hotly contested case, she has pleaded not guilty," defense attorney Robert Weiner said.

Initial speculation blamed snowy conditions for the collision. And the original accident reconstruction showed Zimmerman was traveling about 40 mph -- the posted speed limit.

But the vehicular homicide charge Zimmerman now faces rests on the evidence police found days after the accident; after police obtained this search warrant to extract the so called black box from her mangled sport utility vehicle.

A "black box", like those found in airplanes to retrieve crash data, was attached to the airbags in her Yukon.

Zimmerman said that she had no clue her Yukon was equipped with a black box.

But the 'read-out' from the recorder, obtained by NewsCenter Five, gives critical data about speed, breaking and seat belt use. It shows Zimmerman was traveling as fast as 58 mph -- seconds before the crash.

She claims it's an invasion of privacy.

"It's almost like a government agent sitting in the back seat of the car," Weiner said.

Originally developed to monitor racecars during crashes and make them safer, the technology is helping make all cars safer too.

Nearly 25 million late model vehicles have black boxes. It's news to most drivers, and surprisingly, to some dealers.

Others weren't aware police can also get their hands on the crash data.

"They know the air bag module exists. They just didn't know that the conditions under which the airbag was being deployed were available," Muzi Chevrolet spokesman Glenn Cammerata said.

Zimmerman's lawyer argues that under Massachusetts law, the hidden recording could be illegal.

"You have to have two-party consent," Weiner said.

The Essex County district attorney declined to comment, but others said that the black box is fair game.

"First of all, its not the government putting in something recording information that is then used against you like in a wiretap situation," Middlesex County District Attorney Martha Coakley said.

But even if legal, is this technology invaluable in developing safer cars, reliable enough in a specific accident.

"I haven't found one case in Massachusetts that this technology has been approved by the court," Weiner said.

It is a precedent setting case all drivers should be watching. If convicted, Zimmerman faces up to 2.5 years in jail.