How one can tell when someone is a murderer or not

A first degree murder case was wrapping up in San Francisco.  The prosecutor's case was very unusual in that it was based exclusively on circumstantial evidence.  The husband was accused of killing his wife, but they could never find the body. 

The prosecutor gave his closing argument and demanded that the jury of 13 adults render a verdict of guilty of murder in the first degree.

But the defense counsel had something up his sleeve.  As he addressed the jury he said something most provocative:

"Ladies and gentlemen, this case, so built around circumstantial evidence is really about the concept of reasonable doubt.  Because, you see, as you will soon find out, the victim in this case, Mrs. Dribble, is going to walk through that door in 10 minutes and you will know Mr. Dribble is innocent."

A hush settled over the crowded courtroom as the attorney continued to speak with everyone's eyes constantly glancing toward the door between the jury and the audience.  As time passed toward the 10-minute deadline, people began to shuffle in their chairs and wipe their brows.  But the attorney continued to speak until it was past the 10 minutes.  But, Mrs. Dribble, the alleged victim, did not enter as he promised.

He continued:  "You see, members of the jury, you must have reasonable doubt or you would not have been looking repeatedly at the door.  Your own sense of doubt made you have an expectation of innocence. You must find my client not guilty of the charge of first degree murder."  With that, he closed and thanked the panel.  

The judge gave the jury their instructions and the bailiff led them to the jury room to deliberate on the guilt or innocence of Mr. Dribble.  It took them only 10 minutes and they indicated they had a verdict.

The defense was very sure they would be returning a "not guilty" verdict and he could barely contain his sense of self-assuredness.  He smiled at his client with a warmth that exuded comfort and success.

The jury foreman was asked to return the verdict form to the court's bailiff to be read out loud:

"We the jury find the defendant, Gunther Dribble, guilty of the crime of murder in the first degree."

The defense attorney was devastated and demanded to poll every juror.  But, as he started with the jury foreman, he did not have to go very far.  "Mr. foreman, you, yourself, had your eyes constantly moving toward the door.  You must have had reasonable doubt."

The jury foreman smiled cattily at the defense attorney:  "Yes. That's true, counsel", he responded."but what we noticed also was that your client was the only person in the entire courtroom who never looked at the door."