12 is a good number
Trial by Jury at the Royalty Theatre
The traditional British jury of 12 still makes sense.
For more than six centuries, the English common law understanding was that a jury consisted of 12 persons. This understanding was shared in America as well. At Virginia's convention to ratify the Constitution, for example, James Madison and others argued that several characteristics of the jury, including its size, were so well and widely understood, that it was unnecessary to specify them.
According to Steven Calabresi and Michael Saks, 12 is still the best number for providing "a representative sample of the community, the quality of deliberation, the ability of dissenters to resist majority pressure, accuracy of fact finding" and the quality of verdicts.
If your life is on the line and you're innocent, you have a chance with a jury of 12 in finding one brave and sensible person who won't convict you.