Last week, Washington Post columnist Jamal Khashoggi went missing after entering a Saudi consulate in Turkey to procure a document he needed to marry his fiancée. She waited outside, but he never came out. Khashoggi, a self-exiled Saudi citizen residing in the United States, was a well-known critic of his home country’s government. Turkish and U.S. officials now believe that Khashoggi was killed inside the consulate.

Before he went inside, he reportedly handed his fiancée his two cellphones. But he kept with him a device that might offer some insight into what happened: Turkish officials told Reuters that the Apple Watch that Khashoggi was wearing when he visited the embassy could provide valuable heart rate and location data for their investigation. The Apple Watch was paired with one of the phones he gave his fiancée. However, it is currently unclear what model of Apple Watch he owned or whether its connection to the phone was stable.

Law enforcement in the U.S. has used data from wearable smart devices to investigate crimes in the past. For instance, Connecticut police analyzed the location data from a murder victim’s Fitbit and found that it had been recording movement an hour after her husband claimed she was killed in 2015. And in September, California police were able to pinpoint an eight-minute period in which a woman’s heart rate had spiked and then stopped, placing the murder suspect in the vicinity of the victim during that same time.

But those cases had something in common: There was a body. Christopher Schulte, an expert on digital forensics who teaches at Metropolitan State University and consults on litigation, says the prospect of using a device like an Apple Watch for investigation becomes much more complicated when it comes to a missing person, as is the case with Khashoggi. “Most of the stuff that I come across is specifically around a victim of a crime where we have the body and we have the watch, or where the suspect of a crime is in custody and you’ve taken their watch. The device [in this case] is missing—that’s a new twist,” said Schulte.

Khashoggi’s watch was paired with his phone, which law enforcement officials may be able to use to view the health and location data. But without knowing whether the watch is still on Khashoggi’s person, or what condition it’s in, there is a higher risk of misinterpreting that data. If investigators spot, for example, a sudden cessation in heart activity, that could indicate a death, but it could also indicate that the watch was destroyed or ran out of battery. It’s also possible that the watch was transferred to another person; unless Khashoggi had set up the appropriate security code, the watch would simply keep tracking the biometrics of that other person. Schulte noted, “There’s an issue of authentication. We know that we have these readings, but how do we know that it’s his readings?”

The Apple Watch also won’t necessarily give investigators a second-by-second chart of Khashoggi’s heart rate. Because their battery lives are limited, Apple Watches typically only collect that sort of granular data if a person is exercising. Otherwise, the watch usually only samples a user’s heart rate by measuring it every five minutes. You would only be able to see the heart rate fluctuations indicating a murder if the attack happened while the watch was taking a sample. More advanced versions of the watch and its operating system do have an A.I. feature that can sense when a person is exercising or exhibits a sudden spike in heart rate, so it’s possible that the device would pick up on a victim’s elevated rates during an attack. But since we don’t know the specs of his particular watch, it’s hard to say whether this might be the case here.

It would be most helpful to law enforcement if Khashoggi had one of the later Apple Watch models, because the sensors and features have become more sophisticated. For example, the first-generation Apple Watch doesn’t have a built-in GPS receiver chip. It instead relies on the iPhone’s GPS data, which wouldn’t be very helpful in Khashoggi’s case since he gave his phone to his fiancée. Newer Apple Watches also have a cellular connection feature. Investigators could theoretically have a telecommunications provider hand over data indicating when a watch is connected or unconnected.

“Whenever we’re talking about mobile devices, the forensics that are involved is constantly evolving as the technology changes,” Schulte said when describing the difficulty of surmising how investigators might use the data from Khashoggi’s watch. “Because this stuff is changing, and because the forensics are still being researched, the specific details might not be applicable to this specific scenario.”