No. They're with the other jurors at all times from voir dire to the end of the judge's jury instructions. The last thing the judge does before sending the twelve jurors to deliberate is thank and dismiss the alternates.

It's a very interesting panel that's been selected. Most of the jurors have ties to Penn State, either as alumni or employees. This is expected as Centre County is not big and PSU is huge. There is even one juror, who personally knows Sandusky, though he is an acquaintence and not a friend.