Not buying this...I've been in LE with K9's for 15 years in two agencies and I have never...yes never...seen a working PATROL K9 that is NEVER trained with a choke, prong or an e collar. You never mentioned e collar so maybe you were just referring to the choke/prong methods. Nevertheless, it is quite simply not possible to train these dogs to be patrol dogs with a clicker, a treat, and a pat on the head. Not going to happen.
I'm with you. I've was in LE for 30 years. I've been working with LE K−9's since 1979. Never in all my travels, from one side of the US to the other, or my trips to Canada, the UK and Spain, have I seen a patrol K−9 that was not trained, at least at some point in his career, with either a choke chain, a pinch collar, or an Ecollar. Perhaps lennoxbradley88 was talking about detection dogs who sometimes are trained with these tools? It's a mistake, there are far more effective ways to do it, but most of the country uses OC for this sort of training. But for Patrol dogs, never ...
In fact for many years I've had a challenge available that will bring a finder's fee/training fee of $1,000 to the person who can find me a police patrol K−9 that has been trained only with the so−called "kinder gentler methods." I'll supply the details if anyone is interested. The challenge has been on the Net since about 2000 and no one has ever found me such a dog.