Most police dogs who are used to attack a suspect when needed and bring them down or do searches for drugs are male dogs.
The male police dogs are also not neutered to help maintain the male police dogs aggressive behavior when needed.
Although police dogs are trained to attack someone when needed and bring them down the police dogs when not needed to attack or bring someone down are pleasant to be around.
The police dog will only attack or bring someone down when the officer commands it too.
Some police do use some female dogs though in other things such as search and rescue, locating bombs and sometimes for locating drugs.
But when it comes to attacking someone male police dogs are mostly used.