OnStar said it "complies with its legal obligation to court orders or subpoenas."

In an emailed statement, OnStar said it doesn't "share data with law enforcement absent a court order unless it is necessary to protect the safety of its customers or others." OnStar does provide data to police in cases of stolen cars and can cut off a car's power.

Data gathered from vehicle telematics face roadblocks in the courtroom.

In such cases, the chain of custody is crucial, said Bryant Walker Smith, who teaches law and engineering at the University of South Carolina.

Smith said the chain of custody establishes whether there has been an opportunity for parties to manipulate data.

Questions raised may include:

Who retrieved the system from the vehicle? Then what was done with it?

Who downloaded the data? What was done with the data after the download?

Smith said that can be a "complex" and "onerous" situation.

Then, Smith said, there is the aspect of reliability. Toyota has said in the past that its event data recorders, for example, can't always be trusted.

Smith said vehicle data won't always have the answer. It isn't possible to "press play" and see exactly how a person's entire journey played out, he explained.

And, Smith said, increased interest in data generated by in-car systems may lead to more privacy protections.

"If you look at Supreme Court cases on the criminal side, there is this growing realization from the justices that there is a cloud of information that is very personal to people that is no longer just in their heads, no longer just in their houses," Smith said. "Maybe that sphere around them does deserve some additional protection."

He continued: "Most recently, that has been in respect to cellphones. What is the dividing line between a smartphone and a smart car? Unclear. Maybe there will be a growing judicial notice of this potentially protected space."

With numerous telematics offerings available across the industry, standards will be needed to regulate what information is collectible and the format it's gathered in, said Thilo Koslowski, an analyst at technology research firm Gartner Inc.

If the courts are going to use vehicle data from various manufacturers, Koslowski said, "there have to be some defined guidelines" eventually.

In-vehicle data may have limited value as evidence simply because telematics systems are not designed to serve the legal system, one expert said.

Ultimately, the purpose of collecting vehicle telematics data is to offer safety services and other benefits to motorists, not build legal cases, said David LaBahn, CEO of the Association of Prosecuting Attorneys in Washington.

If the systems were built with the courtroom in mind, LaBahn said, they would track details such as who is driving the car and information about surrounding traffic.

In reality, the tidbits of seat-belt use information or location data can corroborate only portions of an argument. LaBahn said the data still must be combined with other evidence.

But, LaBahn said, some jurors will wonder about vehicle telematics in certain cases, which could put pressure on lawyers to use the data.