Of course, now that we have a national "do not call" list we won't have much of an opportunity to pull off something like this, but a friend of mine swears that he actually did:
The phone rang as I was sitting down to my evening meal. As I answered it, I was greeted with, "Is this Jerrold Buller"? No one calls me "Jerrold" (not even my mom), so I asked who was calling. The telemarketer said he was with The Rubber Band Powered Freezer Company or something like that. Then, a really rotten but brilliant plan just exploded in my brain!
I asked him if he knew Jerrold personally and why was he calling this number. I then said off to the side, "Get some pictures of the body at various angles -- and the blood smears."
I then turned back to the phone and advised the caller that he had called a murder scene, making him a prime "person of interest," and that he must stay on the line because we had already traced this call and he would be receiving a summons to testify in this case.
I questioned the caller at great length as to his name, address, phone number at home, at work, who he worked for, how he knew the dead guy and could he prove where he had been about one hour before he made this call. The telemarketer was getting very concerned and his answers were given in a shaky voice.
I then told him we had located his position and the police were entering the building to take him into custody. At that point, I heard the phone fall and the scurrying clatter of his running away.
My wife asked me as I returned to our table why I had tears of laughter streaming down my face and so help me, I couldn't tell her for about fifteen minutes. My food was cold, but who cares?