I guess I knew at some level of generality that the airbag computers recorded your speed and braking and the like and could thus be used by the police in a DUI-with-injury case (or similar cases). Which is a fancy way of saying that I sort of, generally knew a tiny bit about the concept, but with no real details.
After reading this opinion, I now realize (1) that those "airbag thingies" are called sensing diagnostic modules ("SDMs"), (2) that they're in pretty much every modern vehicle, (3) that they record a lot of detail about your driving, and (4) that the police download the SDM data -- and use it against you -- whenever they feel like it; i.e., whenever the crime is sufficiently major to justify the (relatively small) amount of effort required.
Diaz was convicted of involuntary manslaughter for killing an 18-year old while driving drunk, and she claims on appeal that the SDM data used against her at trial was obtained without a warrant and in violation of the Fourth Amendment. It's not a very sympathetic case in which to make this claim, both given the nature of the offense and the evidence against her. The Court of Appeal pretty much rejects her argument on every ground imaginable; on the merits, harmless error, etc.
You can see where Justice Hollenhorst is coming from. The police already get to "inspect" the "instrumentality" of a crime; e.g., the crashed vehicle. Downloading the SDM data isn't all that different than an inspection. You could (and Diaz's counsel does) analogize this to opening an enclosed container in the vehicle, which it's not clear the police can do. But since the SDM is actually part of the vehicle, you can see why the Court of Appeal reaches the result it does. (You similarly can see why the Court of Appeal property rejects the analogy to the Jones GPS case. In the former, there was a physical trespass to the vehicle in order to install the GPS device. There's no such trespass here, however, since the SDM is already installed and the crashed vehicle is already in the possession of the authorities.)
I will say, however, that I'm not sure why the police don't just get a warrant for this stuff. Which would be really easy to obtain, especially since there's no exigency at all (the police had the crashed vehicle for around a year). The Court of Appeal offers a nonfrivolous answer -- because they don't have to, pursuant to the instrumentality rule -- but that's somewhat tautological, and doesn't really explain why you'd extend the instrumentality to rule SDMs as opposed to limiting it to, say, a purely physical inspection of the property; e.g., looking for blood in the trunk or open beer cans in the front seat.
But in truth, I can't imagine that these warrants would ever really be denied. Moreover, since SDMs produce data that's hardly very private (speed, braking, etc.), I'm not really inclined to broaden the warrant requirement to cover this data. The police are going to get it anyway, it's not really useful for anything other than the prosecution, and adding another unnecessary layer to its receipt doesn't really seem all that necessary.
So I guess I can get on board for the result here. Although I do so with more caveats than -- and not nearly as enthusiastically as -- Justice Hollenhorst.