If police want to snoop through a vehicle's black box data -- even after an accident -- they will have to get a warrant. That was the conclusion Tuesday of the Missouri Court of Appeals, which took up the case of a black box seized from a truck involved in a major collision on July 1, 2015.

Anthony West was behind the wheel of the semi when he came upon stopped traffic and struck a Ford F-150 pickup truck. That rear end collision claimed the life of Margaret Haile, 79. Missouri Highway Patrol investigators used software to download all of the data stored on the semi's electronic control module (ECM). No warrant was obtained since the officers claimed exigent circumstances existed and that West had no expectation of privacy in the data. Grabbing the black box data in serious accidents is standard procedure for the agency.

"The ECM is like the brain of the truck," Sergeant Paul Meyers testified. "It controls all the functions of braking, throttle, transmission... it's also a tattletale on your drivers, you know, to see who is doing what, how fast they are going, and, you know, what their trip summaries look like. So it's kind of a -- for a lack of a better term, a snapshot or a look at how the trucks are operating."

Highway Patrol Corporal Devin Foust claimed West gave him consent to the search, but he did not note that in his report on the incident. The three-judge appellate panel applied the recent US Supreme Court ruling on GPS spying (view ruling) to the circumstances of the case to find the police arguments unconvincing.

"The driver possesses an actual, subjective expectation of privacy in data recorded by an ECM regarding that driver's operation of the vehicle," Judge Cynthia L. Martin wrote for the court. "We can affirm the trial court's order granting the motion to suppress based on longstanding Fourth Amendment jurisprudence involving trespass as a basis to assert a Fourth Amendment violation as recently discussed in the United States Supreme Court's decision in Jones."

The judges noted that it did not matter that West had no idea there was a box recording his every move installed in the truck because the police officer made a physical intrusion into the vehicle to conduct his electronic search. There were no exigent circumstances to do so because there was no reason to think the truck contained anything illegal.

"Though Sergeant Meyers testified about the data that is routinely recorded by a semi-truck's ECM, ECM data is neither contraband nor illegal," Judge Martin ruled. "Sergeant Meyers's testimony underscores that ECM data was seized from West's truck not because there was probable cause to believe that West had committed a crime and that evidence of the crime could be found in the truck, but instead to investigate an accident to determine whether West had committed a crime."

The court refused to allow a warrantless search on such grounds, saying it would "emasculate" the Fourth Amendment.

A copy of the ruling is available in a 150k PDF file at the source link below.