Black boxes
Black boxes

Most cars today contain a so-called "Black Box" similar to those found on airplanes. These boxes continuously record the car's speed as well as what the driver is doing with the steering wheel and brakes.

The box has a short memory, though. The data is continuously overwritten every few seconds. In the event of a crash, the recording stops, preserving the few seconds of data just before and after the impact.

If you were speeding just before the impact -- or if you didn't brake or swerve to avoid the crash -- the recorder knows and its contents could haunt you in a court of law. (Or in the media, as some Toyota accusers found out.)

Getting permission to download data from a car requires a court order, said Michigan personal injury attorney Dan Buckfire, but it's usually not hard to get one.

"It's just general information," he said. "It's not like it was recording where you were going."

In other words, it's just another piece of evidence pertaining to the crash itself, like skid marks or dent damage. Therefore, the privacy issues aren't huge.

If you're the accused, that evidence could work for you or against you. For instance, if you're accused of speeding, the data may show that, actually, you weren't. The challenges are really technical, Buckfire said. This stuff isn't easy to download and few people have the technical expertise needed to do it.

By Peter Valdes-Dapena @PeterDrives - Last updated January 18 2012: 2:12 PM ET
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