Motor Accident case and no action taken by police

I’m writing about the motor accident and death of my sister at Madukkarai, Coimbatore last year (27/12/2015) when the car driven by her husband (my brother-in-law) collided with a truck on the national highway. a) The FIR report from the police holds the truck driver responsible for negligence. However no arrest has ever been made till date. Per Indian law, isn’t it required to arrest the driver? b) The case is currently on queue to appear at the court. The latest we heard was that it will take upto 24-36 months for the court to review. What is the normal timeline? Is there any way by which we can expedite the process? c) I haven’t seen a professional enquiry that has gone into this case. There is no clarity into if the driver was drunk, if his truck was functional (gear/brake) or if they were over speeding. Is there a professional law firm that can represent us locally in Coimbatore and drive the conversation (& if required a private investigation) into the affairs?