The trial began Tuesday for the man who murdered his daughter-in-law so he could videotape himself having sex with her corpse.

Gregory Graf, 54, is charged with first-degree murder — and even his own lawyer does not deny that he murdered 33-year-old Allentown mom Jessica Padgett and then had sex with her body.

Related link: Donations for slain mother near $15K

Philly defense lawyer Jack McMahon, who traveled up to Northampton County to deliver opening statements, admitted in his opening statements that Graf killed Padgett, the Morning Call reported.

However, he is arguing that the crime was not premeditated and only merits a third-degree murder conviction.

"Something snapped in this good man's mind on that date," McMahon said, according to the Morning Call.

Padgett, a beloved daycare worker from Whitehall, Pa., outside Allentown, disappeared on Nov. 21, 2014.

Friends and authorities searched for days for Padgett before her body was discovered on Graf's property.

Padgett told coworkers at Duck Duck Goose daycare that she was leaving to send a fax from her father-in-law's home on Nov. 21. Graf was married to Padgett's mother.

According to the Morning Call, witnesses at the trial said Graf called Padgett repeatedly, insisting she come over immediately to help him with his computer.

After she arrived, he shot her in the head at point-blank range with a handgun.

Prosecutors contended the crime was premeditated and that necrophilia was the motive for the murder.

Hours after shooting Padgett, he reportedly put a plastic bag over her head, and then used two video cameras to film himself having sex with her body.

Jurors will be required to view the footage Graf shot during the trial. Potential jurors were told in advance that they should not agree to serve if they could not bear to watch the video.