March 28, 2018
Once upon a time, not very long ago, the FBI was able to brute-force a phone. No one is quite sure how this was done, but my favorite conspiracy theory is that the phone was cloned to some sort of virtual machine (VM). That VM could have then been copied to as many computers as necessary to run through all the password permutations until the correct password was found. Every time a VM would get locked due to too many attempts, it would simply be destroyed and replaced by another copy.
In the case of exponential delays between attempts, it would be efficient to simply try a password once or twice per VM and move on to a fresh VM to “roll-back” the attempt count. If the original “image” already had a few attempts, creating a significant delay on the next attempt, it would probably be limited to a single password attempt per VM.
However, in the case of criminal-owned smartphones, the police might have to request assistance from the FBI for the brute-force technique that was used to break into the smartphone. Federal law enforcement is notorious for not sharing with local law enforcement. However, if its important enough, the local law enforcement could surrender the case to the local FBI branch.