I got called up for it when I was about 18. I didn't even get to the point of seeing if I was selected for the jury. The way it was when I did it was that they called more people than they needed for the jury, then there would be some kind of random selection to pick the actual jury. As it was, I sat about for two days, then the two girls changed their pleas to guilty (I presume some kind of "deal" was made) so we were all released from duty at that point.