Manhattan jurors Tuesday were shown what prosecutors have said is their “most critical piece of evidence’’ against Daniel Penny — frame-by-frame footage of him allegedly tightening his chokehold on Jordan Neely.

The images were shown at Penny’s manslaughter trial after a Bronx straphanger testified that he jumped in to try to help Penny, 26, restrain the menacing Neely, 30, who at one point looked like he was trying to “escape” the Marine veteran’s chokehold.

The video, an edited version of footage shot by a journalist, showed — frame-by-frame — Penny appearing to increase the pressure of his chokehold as Neely tries to escape.

The footage is what prosecutors have previously called the “most critical piece of evidence” that jurors will see.

“You will see Mr. Neely’s life being snuffed out before your very eyes,” Assistant District Attorney Dafna Yoran had said during opening statements.

Before the video was played Tuesday, witness Eric Gonzalez, 39, testified that he tried to help Penny restrain Neely — and also told Penny to release his grip on the troubled homeless man more than once.

Gonzalez said he had gotten on the uptown F subway train that day, May 1, 2023, while heading to his construction job when he saw Penny holding Neely down.

“Everyone was frantic, saying, ‘Call the cops! Call the cops!’ … I figured one was trying to restrain the other until the cops came,” Gonzalez said of Penny and Neely struggling on the floor.

“I jumped in to try to help.

“‘I am going to grab his hands so you can let go,’ ” Gonzalez said he told Penny, adding he hoped the military veteran would remove his arm from Neely’s neck.

“There was another time where I said, ‘You can let go, I’m holding onto him,’ ” Gonzalez told the jury.

Gonzalez said Neely tapped on someone nearby, indicating he wanted Penny to let go.

“He wanted to be released,” Gonzalez said of Neely, adding it looked like he was trying to “escape.”

Despite Gonzalez’s efforts to get Penny to free Neely, the veteran kept ahold of him, Gonzalez said.

Eventually, Gonzalez said, Neely’s “body went limp.”

Gonzalez said that after the incident, he was “scared” to learn he was initially a suspect in Neely’s death, too.

He testified that even now, he is fearful about his involvement in the case.

“There’s all these protests going on. I’m scared for myself and for my family,” the witness told the jury.

Gonzalez admitted to lying when he was initially interviewed by the Manhattan District Attorney’s Office as a suspect in the troubled homeless man’s death.

Gonzalez, fearful he’d get “pinned for” the murder, said he fibbed to DA investigators, falsely claiming that he arrived on the scene earlier than he actually did and telling authorities that Neely had hit him and that’s what prompted Penny to act.

Gonzalez — who eventually entered into a non-prosecution agreement with the DA’s office — said he told the lies in an attempt at “justifying my actions.”

Gonzalez told jurors that Penny already had a hold of Neely when he arrived at the scene.

Trial testimony indicates that Neely went on a terrifying verbal rant and threatened passengers, but no one has testified that he touched anyone before Penny took him down.

Penny is charged with manslaughter and criminally negligent homicide and faces up to 15 years in prison if convicted on the top charge.

He has pleaded not guilty, and his lawyers have maintained he shouldn’t be held criminally responsible because he was merely acting to protect terrified straphangers from a menacing Neely.