Answer:
A trust and an estate are two separate entities with their own TINs. If a creditor of the decedant has a claim against the estate that they cannot collect because you allowed the check to be deposited to the trust, the creditor could sue you for conversion. If the will directs the proceeds of the estate go to the trust, the personal representative of the estate should deposit the check into the estate account, and then write a check payable to the trust from the estate.