In all honesty though, if this isn't grounds for a mistrial, what is?
This is the correct ruling. Mistrials are not granted as a result of the defendant’s behavior.
Wait ‘til he gets to Walpole and runs into some of the old guy’s family.
Exactly why would it be grounds for a mistrial? Because the jury got an excellent indication of the accused real behavior? Isn't that conducive to justice?
The jury is supposed to be unbiased at the beginning of the trial. If the accused behavior during the trial makes them more likely to come to a certain decision I say justice is being done.
Would you call a mistrial because the accused was unusually nice during the trial?
Generally, a mistrial must be requested by either the prosecution or the defense. The prosecution may not ask for mistrials on the basis of prosecution actions, nor may the defense generally request a mistrail on the basis of defense actions.
If the prosecution wanted to ask for a mistrial on the basis of the defendant's punching the juror, it might be able to, but I can't think of any reason it would want to.
The only reason the defendant might be granted a mistrial on the basis of defense action would be if the defense attorney commited gross misconduct against his client. For example, if a public defender were to punch a juror in the face, a judge may decide that he should call a mistrial, jail the public defender, and move for disbarment. If a judge didn't declare a mistrial, the defendant would likely have an easy appeal on the basis of ineffective counsel; declaring an immediate mistrial would thus benefit a guilty defendant less than would proceeding with the trial and then having it thrown out. It would also make it easier to punish the public defender.