Cops, 12-volt Power, & the Black Box
There is a lot of mis-information circulating among law enforcement and the most common error is that 'killing the powe' will erase all data that they might need for a post-incident investigation.
The 'Black Box' is actually called the Event Data Recorder or EDR by the automotive industry. Within this electronic device, the vehicle use data is stored in what is called a "non-volatile EEPROM memory". EEPROM is Electrically Erasable Programmable Read-Only Memory. This means that the data is NOT lost due to 12volt power being cut by responders at a crash scene.
EDR data can be retrieved and downloaded by properly trained law enforcement officials using proper after-market devices. they have to plug into the vehicle's diagnostic link which is typically under the dash. the other download option that would be used in the case where the 12volt power has been taken away during the incident, is that the PD official would plug directly into the vehicle module that stores EDR data. The information is there within the EDR and does not go away just because of a damaged electrical system or because FD shut down the 12-volt power.
Bottom-Line… Safety first, Cutting 12V battery feed lines WILL ensure no sneak paths of stray electricity exist on crash-damaged vehicles that could power airbags, seat belt pretensioners, deployable roll bars, etc, or cause electrical shorts or fires during vehicle rescue or extrication. In addition, shutting down the 12-volt power does not compromise EDR data