It was the second time Kalila Taylor, now 35, has been convicted of second-degree murder in the death of Curtisha Morning, 17. Her first conviction was thrown out by an appellate court in 2004 because of faulty jury instructions.
Morning was stabbed at least 94 times near Riverhead High School two weeks after she started dating Carl Brown Jr., father of Taylor's first child.
Taylor stood with her arms crossed to hear the verdict, but didn't react. A family member shouted, "It's wrong!" as she stormed out of the courtroom.
Morning's family and prosecutors were relieved. "I needed justice," said Viola Morning, Curtisha's mother. "Curtisha needed justice."
Assistant District Attorney Janet Albertson said she was "very grateful to all the witnesses who came back and put themselves through this ordeal again. Curtisha can continue to rest in peace."
Defense attorney John LoTurco said the verdict did not surprise him.
"We understand the jury's verdict was based on the overwhelming biological evidence, coupled with the compelling identification evidence," he said. "However, the Taylor family believes in Kalila's innocence, and we will prosecute an appeal."
State Supreme Court Justice William Condon said he would sentence Taylor on Aug. 22. She faces a maximum of 25 years to life in prison.
Earlier Monday, LoTurco asked jurors to consider the lack of a confession or a murder weapon in the case and denigrated the apparent motive.
"Curtisha Morning and Carl Brown never even went out in public," he said. "There was no motive for such a savage act."
He said his client's blood, found smudged on Morning's boots and pants cuffs, could have gotten there during a chance encounter in a hospital emergency room a month earlier. Taylor sought treatment after getting bitten on her finger while Morning was visiting her mother there.
Albertson mocked that idea. "There was no magic finger bite, spraying blood all over the place," she said.
Albertson said Taylor's hands were bleeding because the knife likely slipped while she stabbed Morning "over and over and over and over and over again," pounding the lectern as she spoke. "I could do it 94 times, but I'm not going to. It's not rocket science to see that the knife is going to slip."
She was similarly dismissive of a defense suggestion that Morning may have been killed elsewhere before her body was dumped at the field.