[mindcrime]

That said I have sat on a jury where the performance of the prosecuter played a pivotal role in papering over some of the mistakes in the investigation.

I sat on a jury once where the behavior of the prosecutor really hurt his case, because he acted like a total dick and was demeaning and rude towards the defendant. In theory that should have nothing to do with the actual merits of the case, but people being people, it created a certain measure of sympathy for the defendant.

In the end, we acquitted the guy for a number of reasons (mysteriously "missing" evidence, an incompetent investigator, perception that the investigator and victim may have lied, etc.) but the prosecutor's behavior was definitely something that all (or most) of the jurors picked up on and commented on.

I believe that simple things like how the prosecutor (or the defendant) carry themselves, and how they act towards other participants in the trial, can absolutely affect the outcome of cases, at least sometimes.