Courtrooms typically lag in technological innovation. But emerging technologies inevitably creep in when lawyers try to make their cases. Data gleaned from wearables is the latest example.

Last month, data from a wearable was entered as courtroom evidence for the first time. The case involved a Calgary woman making a personal injury claim, following a car accident four years ago. Once a personal trainer, her lawyers have submitted Fitbit to show that her lifestyle has changed dramatically: Her activity levels have since fallen below average for women in a similar demographic.

Some claim that this legal move move may transform accident and personal injury claims. As it turns out, wearable data is on par with any another information when it comes to legal standing.

“Evidence is admitted not because of its source or nature, but because it bears on a fact that is relevant to the underlying legal issue,” said Mike Rhodes of the Cooley law firm. “There’s no intrinsic bar to admitting evidence from wearable tech devices.”

In layman’s terms: Data is data, whether it comes from a document, a drive or a device on your wrist.

The key is authentication: Data must be legitimate, accurate, and related to the party in question. New technologies always undergo extra scrutiny, but if an attorney can prove those three criteria have been met, then wearable data is admissible. And there's the catch. Wearables, by their very nature, can easily be taken off, worn by others, or jostled to create false readings. Thus, wearable data might be easy to undermine.

But there are some crucial instances where wearable data could be useful. “Could they be used to establish whereabouts for an alibi?” Rhodes asked. For example, a combination of GPS location data from a phone and from a wearable could, for example, show someone was nowhere near the scene of the crime on a particular evening. Tyler Newby of Fenwick & West say GPS will always be of high interest. “The whereabouts of a person are often so important, especially in a criminal case," he said. Civil trials are another matter as well: “Could a Fitbit feed be used to show that a cardiologist was negligent in not restricting a patient’s athletic routine?” wonders Rhodes.

GPS information has been used in cases for years, but now that it’s more accessible to consumers, it may find its way into the courtroom more often.

Looking beyond the criminal court at the civil realm, it could also be useful in divorce cases, says Newby. If, for example, GPS data shows a spouse repeatedly visiting the same location for roughly the same amount of time, while heart-monitoring data registers a pulse spike, that could suggest an extramarital affair. Yes, it might also suggest regular trips to the gym, but taken with other data—phone records, for example, or text messages—it could make a case for infidelity.

Meanwhile, in an assault case where someone is claiming self defense, data showing extremely elevated heart rate could support their claim that they felt their life was in danger. Movement data and heart rate could equally show that someone was too calm to be involved in an attack.

The point being: If the data is there, it can be used to fight or bolster a case—and it can pop up unexpectedly. “When it comes to data, you should assume anything tracked is being kept forever unless you know that it’s not,” Covington & Burling’s Simon Frankel told WIRED. And many companies will relinquish what data they have if they're given a court order—just as we've seen with email, according to Lee Tien, senior staff attorney with the Electronic Frontier Foundation.

Let the legal battles begin.