If serving on a grand jury, meeting half a day twice a week for 3 months, when would be the appropriate to disclose this information to a potential new employer while interviewing for a new job?
Let them know ASAP, just be open and honest with them. No need to be secretive about this info. The hiring process will probably take 3+ months anyway, so the jury duty will probably be done with by the time you start.
When I served on Grand Jury we had 2 alternates. The D.A. told us if we had a conflict to call his office. The alternates job was to cover for whoever missed. Can you do the same thing?
I would disclose it on a need to know basis. For me, I wouldn't tell any of them anything that would jeopardize my cadidature until after I was employed and on payroll unless i was certain it wouldnt somehow count against me. Jury duty, vacations, sick kids...nothing.