The language of police and lawyers is one of the most fertile sources of language peeves. With cops, some of the worst tangles arise from an effort to avoid implying as a fact something that is not yet officially "true", such as the constant reiteration of the word "alleged", and others come from narrow special meanings, such as the "unrelated" incident in Mrrzy's example. I'll bet that actually means the stabbing and the "unrelated" incident were not committed by the same person, or were committed by the same person but not for the same reason.