Gait analysis is a more surveillable fingerprint anyway, since it can work with lower resolution cameras. Tag someone on a high res camera with facial recognition and as long as you've seen their gait once, you'll be able to identify them again.
https://news.ycombinator.com/item?id=18401892
I like the comment about the Ministry of Silly Walks.
It's one thing to narrow down a city-sized population to a list of 50 people known to walk with a similar gait, and then follow up with other forms of investigation before drawing conclusions. It's another for a cop to look at the top match and go arrest that guy, as they've done more than once with facial recognition.