If you're both involved in a task and personally probing questions start, either say "Can we focus on the issue at hand, please." or (spoken in a 'matter of fact way') "I'm not really in the mood to talk about this," and suggest current events as an option".Include some sarcasm in the conversation. If they ask you cross-examination style questions, jokingly say "When did you become a cop?", then quickly change direction of the conversation to you, a friend or family member knowing a cop, and start discussing what they think, all the while getting ready for a toilet break.