Civil suit help.....water damage to car?

i have a court trial coming up (a civil court) and i need help...

a brief synopsis....my car was impounded where it was kept for a week. During that week, the sun roof was left open and it had rained followed by a 90 degree sunny weather. Because of the mixture of water and sun, my leather interior hardened to a feel of a plastic plate. Because it's undeniable that the sun roof being left open was at their fault, the only other argument i can think of is the extent of the damage which i must prove. I took pictures of the hardened seats that was visible enough to capture on film, but that seems deniable since my car is 8 years old.
How can i make a claim of the extent of damage left on my car...believe me, the damage to the seat was bad....i noticed it right away from the fading color from black to gray. What was worse was the texture of the leather. Someone please help me.

Since the impound lot took possession, or bailment, of your vehicle then they would be at fault here. The question is do you have the financial resources required to sue them? If it can be done in small claims court I would go that route, seems like a slam dunk to me.

In some states, a good lawyer can find different laws to sue them under and therefore pursue attorneys' fees as well as actual damages.

The testimony or written statement of an expert, such as a car repair person or better yet someone from a dealer repair office, would go a long way toward helping prove that the damage was caused by the rain while they had the car. That being said, whether they could actually be found at fault would depend on the regulations in your state/city. Did you try to file a claim with their insurance first? They would actually be the ones to pay the claim if they lose the case anyway.