In most states it has to be unanimous, yes, although some research suggests it matters less than you think. Also, you aren’t home free. A non-unanimous verdict means a mistrial and the prosecution can just try you again.I have no direct experience of criminal trials, but I was under the impression that majority verdicts were generally accepted. So in the US you can bribe one jury member (or one fuckwit on the jury who has an unconditional love for the police in this case) and you're home free? Weird.
Did a quick UK-centric google and found this:
Jury Trial - How Your Fate is Decided - Moss & Co Solicitors
Jury trial in the crown court. Moss & Co explain the ins and outs of trial by jury. case preparation and the taking of verdicts.www.mosslaw.co.uk
Interestingly enough, some research shows that group decision making like this can lead to more guilty verdicts. Basically the logic is that if you vote guilty your vote only convicts of 11 other people agree with you, which removes some of the burden of responsibility.