Being capable , competent, for ALL jurors is a prerequisite. From personal knowledge I don't think this is practiced at the moment. Don't see why jurors of any age should be excluded, provided they are competent, and fit enough to attend.
Having served on two juries in the past, I lost my confidence with the jury system. I still feel I cannot give details about the specific cases; enough to say that most of the people I was with thought it was like "Perry Mason".That the barristers had personally been involved in the case, and that the evidence being given had to be proved to the last iota. They couldn't understand that proof was often a balance of probabilities, that they had to decide upon.
One person was found not guilty, and from the look on his face he couldn't believe it either.I could have been in the jury room all week and would have made no difference, so I went along with the majority, to have stuck it out for a few hours until the judge would have accepted a majority verdict, would not have affected the outcome.The other person was found guilty, after I had proven that he could have been guilty, and on balance was. Logic prevailed and the "TV crime series" followers came onboard.I found the whole experience to be very "hit and miss"and was not very satisfied with the jury system at all. It may be different with a group of different people, which again is not reassuring.
A previous time many years ago, when we were converted from towns gas to natural gas, (The relevance of this is not only to give a time line, but also to indicate that the case was involving the theft of gas jets) Was different, in as much as the judge told the jury that the man was not to be found guilty. He had been charged with the wrong offence. However he would, we were told, be up before him again and would doubtless be imprisoned.