A "black box" data recorder from a defendant's car may provide evidence in an upcoming Northern Kentucky trial in a case that raises intriguing questions about privacy and the dependability of technology.

Should such recorders be considered safety devices - a logical extension of seat belts and air bags? Or are they intrusions into personal privacy, allowing the police to document driving infractions they did not witness?

Such questions may come up in January during the Kenton County trial of Lloyd Robinson, charged with manslaughter in the May 2003 death of Kentucky Fish & Wildlife Resources Officer Doug Bryant. Bryant was killed after both men's vehicles crashed during what police said was a high-speed chase along Interstate 75.

Data recorders, capable of recording speed and braking times, are installed in about 15 percent of the country's 200 million passenger vehicles, and the number grows with each new model year. Prosecutors say data from the recorder in Robinson's car confirmed witness accounts that he was going 70 to 80 mph at the time of the crash. But the court has ordered data from a recorder in Bryant's vehicle turned over to the defense for comparison purposes.

Therein lies one of the difficulties posed by this technology. The truck has an older-model recorder that might not be as reliable, particularly after having been in a crash, as the one from Robinson's car. Will conflicting data ratings be treated in the same way as conflicting testimony from human witnesses?

Civil libertarians also make the argument that many drivers don't know their vehicles have such recorders, or that they could be incriminating themselves every time they step on the gas. The National Transportation Safety Board has recommended that recorders be mandatory equipment in all cars, a recommendation that so far has been blocked by the National Highway Traffic Safety Administration. The latter group says a regulation is unnecessary because the industry already is moving in that direction.

Meanwhile, car buyers should be sure to check their vehicle's equipment list and remember that how they drive may be monitored without their knowledge.