Friday, February 8, 2013

CA appellate court allows warrantless use of speed/braking records from car's airbag module (SDM)

In another first impression case, a California appellate court ruled that an individual has no reasonable expectation of privacy in the data recorded by a car's sensing diagnostic module (SDM), which is part of the airbag system. Therefore, the court upheld the police's actions to retrieve that information from a car that was lawfully impounded after an accident. The case is People v. Diaz, __ Cal. App. Ct. __ (Feb 6, 2013), and a copy of the opinion can be found: here.

The "main function of the SDM is to deploy the air bags. The SDM has the secondary function of recording throttle, speed, application of brakes, and transmission position." In this case it was used as evidence to prove the speed of a vehicle involved in an accident resulting in death (the driver was also intoxicated). The defendant argued that an individual has a reasonable expectation of privacy in that information, and that the police's actions to cut her carpet to get to the module, and then download the data, was a violation of the Fourth Amendment. As mentioned above, the car had been impounded after the accident, and was essentially totaled. The defendant attempted to make an appeal to United States v. Jones in her argument to no avail. The court quickly dismissed that argument, stating "the trespass theory underlying Jones has no relevance and, as the trial court aptly pointed out, the purpose of the SDM was not to obtain information for the police. Thus, Jones is not helpful to defendant."

The holding of the case turned on the instrumentality of crime exception to the warrant requirement, stating that: "In this case, defendant's vehicle was itself an instrumentality of the crime of vehicular manslaughter. Defendant concedes it was lawfully seized. Consistent with the California Supreme Court cases discussed above, the officers' 'subsequent examination of the [vehicle] for the purpose of examining its evidentiary value [did] not constitute a ‘search’ as that term is used in the California and federal Constitutions. [Citations.]'"

Regarding the expectation of privacy, the real interesting portion of the court's holding is below:

As the trial court pointed out, the specific data obtained from the SDM was the vehicle's speed and braking immediately before the impact. We agree that a person has no reasonable expectation of privacy in speed on a public highway because speed may readily be observed and measured through, for example, radar devices . . ., pacing the vehicle . . ., or estimation by a trained expert . . . . Similarly, a person has no reasonable expectation of privacy in use of a vehicle's brakes because statutorily required brake lights (Veh. Code, § 24603) announce that use to the public. Thus, defendant has not demonstrated that she had a subjective expectation of privacy in the SDM's recorded data because she was driving on the public roadway, and others could observe her vehicle's movements, braking, and speed, either directly or through the use of technology such as radar guns or automated cameras. In this case, technology merely captured information defendant knowingly exposed to the public—the speed at which she was travelling and whether she applied her brakes before the impact. 
We conclude there was no Fourth Amendment violation in the admission of SDM evidence.
I was unaware, until reading this case, that such information was stored on a device in cars equipped with airbags. It is a very interesting case, and I believe the court resolved it correctly. An attempt to pull Jones in to inject the ideas of "mosaic theory" and trespass was an interesting move by the defense, but knowing someone's location and tracking their every move is much different than reconstructing their speed and braking. GPS tracking can reveal much about a person's life. Speed and braking can pretty much only tell you if that person has a lead foot or rides the brakes.

New York dealt with a similar case in 2004 (which the court mentions), People v. Christmann, 776 N.Y.S.2d 437 (Just. Ct. 2004), resulting in the same outcome.


  1. "In this case, defendant's vehicle was itself an instrumentality of the crime of vehicular manslaughter. Defendant concedes it was lawfully seized.

    This is kind of a key section to understanding the post. I had (incorrectly) assumed that the information was gathered from a cart that had not already been lawfully seized.