How to expedite the case on chain snatching attempt filed in the court

Hello, My mother was a victim of a chain snatching attempt 3 years ago. The chain snatcher left his mobile at the incident. She filed a FIR, the the accused has been identified.The court has been calling her as witness for attending the court hearings. She attended few and others she could not. The reason behind that is she stays with me most of the time in U.S.A and the case has just been dragging for these years. I have not been able to attend the court hearings so far, so my mother had to attend them alone. What can be done to expedite this and end this. I see no reason why my mother has to bear all this . How many times do you need to come for witness.