Re: actual techniques used by police
I can confirm that there is at least one senior policeman in Yorkshire that knows Aikido as he's my teacher.
He has used Aikido in the street while working. His main criticism of it was that throws were bad since the suspect can get away, harm others and/or sue the officer for GBH. Pins are the best things but one needs to be careful not to break anything. Again, see my inumerable list of posts on "reasonable force"...