I hope this isn't homework you're cheating on. Reasons: Understanding criminal behavior, "profiling" to figure out who the criminal is; understanding mental illness, because police have to deal with a lot of mentally ill people; helping police learn how to de-escalate conflict, by understanding psychology better.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.