The FBI has agreed to share details of how it unlocked an iPhone — but with local police rather than Apple.

The bureau’s court battle to force Apple to disable a security feature on the iPhone of the San Bernadino shooter came to an abrupt end this week when officials confirmed they had found a way to bypass the problem of 10 failed login attempts leading to a data wipe. The case has now been vacated.

Exactly how the FBI pulled it off hasn’t been revealed other than that it had help from a third party. It’s widely speculated that it was Israeli firm Cellebrite.

Now prosecutors in an Arkansas murder case have asked the FBI for its help in accessing data on a phone belonging to one of the accused, a request that’s now been accepted.

There’s no guarantee that whatever technique the FBI used (or commissioned) for the San Bernadino case will work here. The phone in that case was an iPhone 5c, which has slightly weaker security than later models.

This still leaves the central legal argument of the FBI-Apple case unresolved, namely the FBI’s case (upheld in an original court hearing) that the 1789 All Writs Act could force Apple to create a backdoor against Apple’s counter-argument (which has not been ruled upon) that the FBI demand hadn’t met the burden of being “necessary and appropriate”, particularly taking into account the potential consequences for other users if the backdoor leaked.

It seems inevitable that argument will be revisited given the American Civil Liberties Union has just revealed that the government has used the All Writs Act 63 times since 2008 in cases relating to secured data on iPhone and Android handsets.