The initial buzz that followed the news that General Motors Corp. is introducing “black box” technology into its cars centered on the improvements in safety and crash data that such technology will bring. Some plaintiffs’ and defense lawyers involved in auto crash litigation echo this positive message, saying that they look forward to more efficient, accurate resolution of car-crash liability cases. But others, concerned about how the devices’ information will be used in court, fear that these black boxes may turn out to be Pandora’s boxes.

“Will this be put to bad use?” asks Larry Pozner, the outgoing president of the National Association of Criminal Defense Lawyers. “Inevitably. “It starts with ‘We have something that will make life safer’ and it ends with ‘We have something to invade your privacy,’ ” says Mr. Pozner.