Ha ha

My retirement magazine came up with this one which I liked.  Actually, I've thrown the magazine away by now, but this is how I remember it - 
A barrister is defending a man on a charge of murder.  No body has ever been found.  He decides to use this fact to play a trick on the jury.  "Ladies and gentlemen" he says "I will prove the defendant is not guilty.  In precisely one minute the person supposed to have been murdered will walk through that door".  The jurors' eyes all turn to the door indicated.  A minute passes and nothing happens.  "OK" says the barrister "I made that up.  But the fact you all looked at the door shows that there is reasonable doubt in your mind that there ever was any murder.  I invite you to acquit".  The jury go out to consider their verdict and come back to announce they have found the defendant guilty.  Later the barrister buttonholes the jury foreman.  "How could you have convicted?" he says "I saw you all looking at the door".  "Yes" says the foreman "but your client didn't!"