One way to find out if he had a will is to contact the clerk of court in the county where he resided at the time of his death. Wills are handled in the probate division and the probate process is public. They may even have the information available online. If his estate is being probated you can contact the attorney who will update you if you are a beneficiary and may be able to inform you If your stepmother is going to be prosecuted. After you have this information, you should contact a local attorney to protect your rights.
Please be advised that the foregoing discussion is a generalized and hypothetical answer based upon incomplete facts and is not intended to serve as legal advice to you, nor should you regard it as an attorney-client communication or as creating an attorney-client relationship. If you desire legal advice concerning the situation you have described you should contact an attorney who has substantive experience in the fields pertaining to your question.