After a deadly car crash, Georgia police downloaded data from the Event Data Recorder on Mobley’s car to determine his speed before the crash, using that to level more severe accusations against him. Georgia has contended that this was legal under the Fourth Amendment’s “vehicle exception” allowing searches for physical items, but the ACLU believes this doesn’t count for digital data. It likened this to requiring a warrant for phone data — just because the device holding the data is obtainable without a warrant doesn’t mean the data is also up for grabs.

There’s no certainty that the court will take the ACLU’s briefing into account. The decision could have a significant impact on how police search car data, though. And the verdict is likely to become more important over time as connected and self-driving cars take hold — they may store very detailed daa about you and your driving habits.