Jury Duty

Got a jury summons from the mail today. Ok, this would be an interesting experience, the thought of witnessing a real live court room drama plus the responsibility of having the life and future of a man resting on my hands (and the hands of 11 other jurors) excites me. However, when I was about to fill up the form.... the Citizenship question disappoints me, I know the answer from that disqualifies me for serving. Husband confirmed that only US Citizens are eligible for jury duty, oh, well, why did they send me a summons then?