Sorry to hear about your dad's unfair treatment.

Wish I could help you more but I don't have a law background. However, in the US, I believe the judge is much wiser and open minded than the police officers. So in the end the judge will rule your dad is not guilty. However, you may ask for a lawyer to sue the company and the police to get some compensation for your parents. It must have been very hard to be treated like this with cancer and diabetes. Good luck.