Jurors in the stairwell-shooting trial of NYPD Officer Peter Liang for manslaughter all ran a hands-on test of the trigger on the gun that killed Akai Gurley, but failed to reach a verdict during their first full day of deliberations in Supreme Court in Brooklyn on Wednesday.

The trigger-resistance of the gun is a key piece of evidence in the 2014 shooting. The defense contends Liang’s weapon fired accidentally when he entered a darkened stairwell at the Louis H. Pink public housing project in East New York and flinched at a sound. Prosecutors say he panicked and fired on purpose.

Some of the jurors had handled the gun during the trial, but after they asked for it again in a note, Justice Danny Chun let each of the 12 test it out in the courtroom, one-by-one squeezing the trigger until the hammer clicked. An officer racked it to reset it for each juror.

Jurors also asked for readbacks of key testimony by Liang, his partner and Gurley’s girlfriend, and recordings of radio and 911 calls. It was the second day of deliberations.

In addition to manslaughter, Liang, 28, is charged with assault, reckless endangerment, criminally negligent homicide and official misconduct because he failed to give CPR to Gurley, 28, after a bullet from the officer’s gun ricocheted off a wall and hit him on Nov. 20.

Deliberations are scheduled to resume on Thursday.

Meanwhile, police said they’re investigating after a man appeared to wave a handgun behind a television news reporter during a live broadcast outside the courthouse Wednesday, according to The Associated Press.

advertisement | advertise on newsday

It happened shortly after noon as a WNBC-TV’s Michael George reported on the Liang trial as he stood in front of Brooklyn Supreme Court, the AP said. The man appeared to wave the gun behind George.

An NYPD spokesman said it’s being investigated as a menacing incident and have released a video of the suspect.

In August, reporter Alison Parker and video journalist Adam Ward, of Roanoke, Virginia, TV station WDBJ, were fatally shot during a live broadcast.