Dear Kapoor,
You have a good case for defence and I don't know whether you have already filed a Quash Proceedings in the High Court challenging the proceedings initiated by the complainant in the criminal court. The main ingredient is that the cheque issued should be a legally enforceable debt, in your case it is only towards the security your son had given it to the finance company and it is being misused by them, once you prove this defence then you are out of the criminal proceedings of the case. However, the finance company can be left with an option of initiating the civil proceedings for recovery of amount but the law of limitation will come to your rescue. Go ahead with your case even in trial you can prove the malafide intentions of the finance company in manipulating the facts and projecting the untrue facts before the court to get benefit by illegal means.