The onetime fiancée of disgraced ex-NYPD cop Michael Valva would unload “vicious outbursts” at the cop’s autistic son before the 8-year-old boy was found frozen to death in the couple’s Long Island home, a witness testified at her murder trial.

Angela Pollina, 45, who is charged in the Jan. 17, 2020 death of little Thomas Valva in the East Moriches home, was in the habit of cursing and screaming at the boy, piano teacher Tina Licari testified Tuesday, Newsday reported.

“I would hear almost like [a] zero to 100 explosion,” Licari, who gave weekly lessons to one of Pollina’s daughters, told the jury on Tuesday. “She’d be screaming.”

Licari said Pollina and her ex-cop beau even mocked Thomas’ autism, mocking him when he didn’t answer questions they shouted at him.

“‘That’s right because you can’t talk,'” Licari recalled Pollina screaming. She said Pollina then snickered at the defenseless boy.

Pollina is charged with second-degree murder and child endangerment. At the start of her trial Monday, Suffolk County prosecutors told jurors that Pollina is as guilty of the boy’s cruel hypothermia death as the disgraced former cop.

Michael Valva, 43, was found guilty of murder in the case last year and sentenced to 25 years to life in prison in December.

Prosecutors said Valva locked both his sons in a freezing and unheated garage as punishment after Thomas soiled himself.

First responders testified at the ex-cop’s trial that he showed no emotion as paramedics tried desperately to revive Thomas as he lay motionless on the floor.

During opening statements at Pollina’s trial, prosecutor James Scahill said Pollina bears as much responsibility because she didn’t lift a finger to help the youngster after his father doused him with cold water outside in 19-degree weather.

Scahill called Pollina’s treatment of Thomas and his brother Anthony, then 10, “evil, wicked and inhumane.”

Defense attorney Matthew Tuohy argued that it was Michael Valva, not his client, who bears the burden of the boy’s senseless death.

“It was Valva who put the boys in the garage — not Miss Pollina,” he told jurors.

Tuohy said Pollina is expected to testify during the trial.