Have there ever been any studies of jury performance based on selection rules for the juror pool? For example, I sat around several times at Cook County courthouses waiting to be called, and the evident quality of potential jurors was pretty decent: a lot of guys in business suits reading the WSJ. Among potential jurors in LA County courthouses, however, you have a lot of people sitting around staring blankly. My impression is that this is due to where names were drawn from at the different periods in different places: voter registration roles in Cook County in the 20th Century, Department of Motor Vehicle rolls in Los Angeles County in the 21st Century. There are a lot of opportunities for social sciences studies here, such as natural experiments of the impact when the source of the jury summons gets changed.
In general, however, most Americans don't seem to want to think about just how badly juries often perform.