Most people have heard of the heavy-duty “black box” every airplane carries, recording every technical detail in case the plane crashes or another problem needs investigation. But few people remember that cars have black boxes too.

Recently, Georgia’s highest court said that police cannot use information from a car’s black box as evidence in court, at least not without following the right steps during their investigation.

Car’s data downloaded with no warrant or probable cause

The case before the Supreme Court of Georgia involved a man in a 2014 Charger driving down a road in Henry County, about 25 miles south of Atlanta. A 1999 Corvette pulled out of a driveway and the collision between the two cars killed the driver and passenger of the Corvette.

No evidence or witness statements gave any hint that the driver of the Charger had been speeding. Still, the police downloaded the data from the Charger’s black box, and it suggested the vehicle was going nearly 100 m.p.h. at the moment of the crash.

They charged the Charger’s driver with vehicular homicide and the driver got seven years in prison.

Fourth Amendment rights apply to your car’s data

The driver, now a prisoner, appealed his case through Georgia’s courts to Georgia’s high court. The court heard arguments that police could, and did, get a warrant for the data the day after they downloaded the data. No harm came, the arguments went, from looking a little early.

The court rejected these arguments, countering that if police look for incriminating evidence and then ask for a search warrant after they find it, search warrants lose their meaning and purpose. The court ruled the search violated the driver’s rights guaranteed by the Fourth Amendment to the U.S. Constitution.

It promises Americans the right “to be secure in their persons, houses, papers, and effects” and requires a warrant with “probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Nearly every car on the road today has a black box

According to USA Today, 96% of new cars already had a black box back in 2013. As of September 2014, every new car had to have one by law. Unless your vehicle is much older than that, there is a good chance you are driving with one on board.