Killing suspects in custody is not, so far as I know, is a technique the police department endorses. If you misuse an approved technique and the suspect dies because of it then the fact that the technique was approved should be irrelevant. The officer misused the technique and killed a man while misusing it so he should face charges.
I don’t know if you killed him or not, did he?
Misuse a technique and whose judgment is ? a lot is left to the cop’s discretion. We shall see.