A perp with a long rap sheet who was convicted of killing an 80-year-old bodega owner may have found a novel way to delay his inevitable sentencing — by denying that he was in fact the man who was convicted of a raft of past crimes, including robbery.

Mark Thomas, 42, was set to learn his fate on Monday, but decided to hold things up by taking the unusual step of denying that he is the man who was convicted of three of his prior felonies.

The denial came as Brooklyn Supreme Court Judge Ruth Shilllingford asked Thomas if he is indeed the man who was convicted of his past offenses — a routine step at sentencings for defendants who were convicted of past felonies.

“Your client said he is not the person who was convicted,” Shillingford said to defense attorney David Walensky, who told The Post following the sentencing that, in his 35 years of practicing law, Thomas’ case was only the second time he’d seen a defendant pull a stunt like this.

The judge kept her cool and postponed sentencing for Oct. 9, which will give Assistant District Attorney Jamie Begley time to track down transcripts and certificates of conviction for Thomas’ old cases — and add an extra month to Thomas’ stay on Rikers Island.

Walensky said not owning up to past felonies at sentencing hearings “doesn’t really benefit” defendants if there’s no reason to deny them.“Either they don’t understand or they just want to be a pain in the butt,” Walensky said.

Thomas was convicted last month of manslaughter, attempted murder, criminal possession of a weapon and reckless endangerment, but managed to beat a second-degree murder charge, for the 2017 killing of Abdulla Yafaee in his East New York bodega. Thomas faces 25 years to life in prison.

The shooting was something of a capstone for a long criminal career for Thomas that goes back decades and includes some 20 priors, including robbery and illegal weapons possession.