Scot here. I've been called to jury service on several occasions, the last in the 1990s. Our system calls for 15 bods, not 12, and permits a " not proven " verdict. Unfortunately, I can't tell you anything about the quality of the juries, as I have not been permitted to serve, although I have been " balloted " more than once ( my name popped out of the hat ). The difficulty seems to be my appearance, which occasions a weary " Please sit down " from the fiscal-depute ( prosecutor ), who is ( or was ) permitted to challenge anything that appears to be able to tie its shoelaces.
Still, days out in court have not been wasted: I have heard a judge define a " reasonable doubt " as being not a fanciful or metaphysical doubt but rather a doubt of the sort that might give you pause for thought in your everyday affairs.