Most middle-class, law-abiding people think of the police as being on their side, protecting them from criminals. Hence if a police officer should, for any reason, request to talk to us about a crime or request a search of our car, home, or person, we would likely consent, thinking that it must be due to some misunderstanding that will soon be cleared up and would likely be a good story to tell one’s friends later.
It turns out that this is not a good idea and that you should never voluntarily consent to talk to the police or agree to a search.
See this video by law professor and former defense attorney James Duane on why he will never talk to the police under any circumstances nor advise his clients to do so. It does not matter if you are completely innocent and completely truthful. [Update: The response by the police chief at the end says that Duane is right, and also talks about the tricks they use to get people to talk.]
This was one of those rare cases where my mind was immediately changed simply by hearing an opposing argument.