Also, if a prosecuting attorney "packs" the jury with idiots...
The prosecuting attorney doesn't get to solely select the jurors. Jury selection is a kind of game played between the prosecuting attorney and the defense attorney. Both attorneys are attempting to select the jurors they think will best suit their case - and they each get to make seven selections for the preliminary jury.
Six jurors and one alternate selection of their choice. Between the prosecutor and the defense attorney, that's how you get to fourteen. Then they get to wrangle over what seat you're assigned in the jury box. You are put into a specific seat as agreed to by both attorneys.
So, neither side can "pack" a jury.
If your lawyer is so bad at voir dire that all 14 members of the jury know nothing about guns, you probably don't have much of a chance winning your case regardless of the circumstances surrounding the shooting....
Again, the defense attorney doesn't get to solely pick jurors. There is an extensive background document that you fill out when you are called for jury duty. The one I filled out was 12 pages long, and included questions about hobbies, organizations you belong to, voting party affiliation, job, etc.
Both the prosecutor and defense attorneys will already know that one of your hobbies is shooting, and that you belong to the NRA. They will pick you or object to you being on a jury based on the background information - questioning you may not even happen during jury selection.
Let me give you a real life example.
In one week, I was selected as a juror for four (4) separate trials. After the first two - I understood the game. I was being selected as one of the 12 jurors by the prosecuting attorney so that I would use up one of the defense attorney's uncontested juror objections.
This was solely based upon the information in my interview form. Job - engineer. Hobbies - trap shooting, pistol shooting, precision rifle shooting. Organization membership - NRA. Etc.
The prosecutor loved my background as it was an instant disqualification from the defense attorney. Both of attorneys, with no interaction with me, figured I was a "Hang all of them" kind of guy.
Which, as an engineer, couldn't be further from the truth. Engineers always want all of the information involved with an issue before making any kind of judgment. But, based upon my background information - I was never given that chance.
For each trial, I was purposely seated in the front row across from the defenses' table. In one case, every juror (except me) and five alternates were thoroughly questioned. I was never questioned because my outcome was predetermined - I was going to be disqualified. The prosecutor knew it and the defense attorney knew it - so, no need to ask me questions.
Of course, the defense attorney does the same thing - select specific jurors that they know the prosecutor will automatically object to because of their background information.
But, to be selected for, and disqualified from, four separate trials in one week has to set some kind of record. In fact, I was let out of the second week of jury duty specifically because I had been selected four times.
When the attorneys have a pool of over 200 jurors to select from and I get selected four times - that points to the prosecutor using me for a specific purpose - disqualification.
That is how jury selection really works...and what they're going for is not "packing a jury," and not including people educated in a specific area. What happens is each side agrees to the jurors that they have the least objections to.