I have been called on for jury duty before THREE times,not exactly the same thing but I got out of it every time.
first time I got a doctors note [I was pregnant] second time it was for child care reasons ,third time was for medical reasons of a different kind!
How serious is the crime? do they REALLY need you.
if you can think of a good argument why you cannot make it,you may have a chance,but then again,it would depend on how badly they need you to testify.