Trial begins in 2015 slay of officer in Qns.

THE TRIAL of an accused Queens cop killer opened Friday with a litany of damning evidence: Three witnesses, DNA on the murder weapon, and a ballistics match.

Demetrius Blackwell, 37, wore a white button-down shirt, black pants and handcuffs as Assistant District Attorney Daniel Saunders identified him as the coldblooded killer of NYPD Officer Brian Moore.

Saunders recounted how Moore, 25, (photo, right) and his partner stopped ex-con Blackwell (photo, left) on suspicion of carrying a gun, with the routine encounter turning deadly in mere seconds on May 2, 2015.

“Officer Moore began to open the (car) door and said the last words he would ever say: ‘Police. You got something?’ ” the prosecutor said.

Blackwell responded “Yeah, I got something” before pulling the silver handgun and pumping two bullets in Moore’s head. The plainclothes cop, the son of a retired NYPD sergeant, died two days later.

When Blackwell was arrested 90 minutes after the 6:15 p.m. shooting, “he began to cry” in the back of the police car, said Saunders.

Three Queens Village residents identified Blackwell as the gunman, while ballistics evidence and his own DNA linked him to the murder weapon.

The slain officer’s father Raymond and his mother Irene listened as the courtroom echoed with the details of their son’s execution. His mom wore a small replica of Brian’s badge on a necklace.

Defense attorney David Bart acknowledged the killing of the officer before telling the jurors, “That’s one of the few things I will concede to you.”

The lawyer questioned the validity of the DNA evidence linking his client to the murder weapon and questioned the reliability of the witnesses.

“This is a complex and difficult case with a lot of emotion overshadowing it,” said Bart in his opening statement.

“But you cannot and should not hold Mr. Blackwell accountable because you will find the evidence does not support it.”

Bart also suggested brain surgery two years before the shooting negatively affected his epileptic client’s day to day equilibrium.

Patrolmen’s Benevolent Association head Patrick Lynch, speaking after the opening statements, ripped the defendant and the defense lawyer.

“This is a cold-hearted killer that thought he was a tough guy in the streets . . . and now hides like a coward behind his attorney,” said Lynch.