A Manhattan prosecutor stood before a jury yesterday pulling a rope around her neck with one hand and holding a timer in the other — to prove it takes both brutality and patience to strangle someone to death.

“And he’s still pulling,” Assistant District Attorney Leila Kermani told jurors in closing arguments in the 2009 murder of popular CUNY professor Edgard Mercado. “It’s already been a minute and a half, and he’s still going,” she said.

Defendant Davawn Robinson, 24, of Paterson, NJ, has admitted he strangled Mercado with Mercado’s martial-arts uniform belt, but insisted the death was accidental.