A search warrant shows authorities suspect a Utah doctor and lawyer killed his wife by giving her a lethal combination of drugs days after she underwent surgery.

The Deseret News reports that the search warrant filed in 4th District Court earlier this month shows authorities believe Martin MacNeill, who is serving time for identity fraud, had the motive and opportunity to kill his wife, Michele, in 2007.

An investigation is ongoing and he has not been charged in her death.

An initial autopsy attributed Michele MacNeill's death to natural causes after she was found dead in a bathtub in her home.

The new warrant states recent information led a medical examiner to believe drugs found in her system could have been lethal and question if she took the medications willingly.