From what I’ve read, an employer can’t legally fire you for attending jury duty, although they don’t have to pay you.
I’ve been called before but never had to serve more than a day. However, a grad student friend of mine was called, had already deferred once before, and is concerned that if he has to serve for an extended period, it would set his work back so that he couldn’t graduate in time, and his department told him that he can’t request another extension.
Can you be dismissed from a program for fulfilling your civic duty?
This is in the US, and the university is public if that has any bearing.
* UPDATE * - I'm really glad that I asked this question. Today I received a summons for jury duty, and I am to appear in court at the EXACT date and time of my defense. It can happen to you!!!
* UPDATE 2 * - Here is how I dealt with it. I told my advisor that I had been called and asked if he would contact someone in the university administration to write an official letter asking to excuse me from jury duty on that day. A few days later, I was given a letter to that effect. The county I live in has a Jury Commission where you can go and "plead your case" to be excused. I went to the Jury Commission and brought my letter, at which time they asked me when I would be able to serve. I gave alternate dates (after my planned deposit date ;-) ), which they accepted. The Jury Commission really appreciated that I had brought an official letter from the administration, as they had received excuse letters from doctoral student's advisors, and rejected them. Having something from the university administration itself carries much more weight. Thankfully, it all worked out!