Kasim Khuram, 23, plead guilty to burgling the co-operative undertakers on Walsall Road, Great Barr, Birmingham on 11 November, the Birmingham Mail reported.
Mr. Khumar did not stop having sex with the corpse even as the burglar alarm sounded, according to the Birmingham Mail.
A Birmingham Crown Court judge said that Mr. Khuram faces "substantial" jail time, with sentencing adjourned until the end of January when the offender can undergo a psychiatric evaluation.
"You must be under no illusion that you will receive a sentence of imprisonment for your offending in this case — a substantial sentence of imprisonment."
Mr. Khuram was sectioned after his arrest, the court found. Sentencing was adjourned so that Khuram's defence could submit a medical report to court officials.
A Central England Co-operative spokesperson said: "Our primary concern is for the families we serve and the welfare of our funeral colleagues who have all been deeply affected by this incredibly disturbing and unprecedented event."
"The security measures at Great Barr are such that the alarm alerted the police, who were thankfully able to apprehend the suspect at the scene."