The former Marine who taught Daniel Penny how to apply a chokehold was called to testify at his trial on Thursday.

Joseph Caballer was not present when Penny, a 26-year-old Marine veteran, placed Jordan Neely in a chokehold on a New York City subway car last year. On the stand, Caballer referred to photos and videos of the incident to make his assessment that Penny incorrectly performed the chokehold he taught him, which cuts off the oxygen to the brain in about eight seconds, The New York Times reported.

Caballer testified that the videos and images he saw appeared to show Penny holding Neely for several minutes, though Penny has denied that he was applying pressure to Neely’s neck the entire time. Caballer testified that, as Neely shifted against Penny, the original chokehold could have become an “air choke,” which can “cause injury to the trachea or windpipe” and is not taught by the Marines.

Also on Thursday, jurors were shown Penny’s videotaped interrogation with police following the incident on the train. In the video, Penny tells two detectives that he wasn’t “trying to kill the guy,” referring to Neely.

“I wasn’t trying to injure him. I’m just trying to keep him from hurting anybody else,” Penny said in the video, according to the New York Post.

“That’s what we are taught in the Marine Corps,” Penny added, referring to his attempt to protect other people from Neely’s alleged threats.

One of the detectives present during this interrogation, Brian McCarthy, testified that he didn’t tell Penny that Neely had died at that time.

MATT WALSH’S ‘AM I RACIST?’ NOW STREAMING ON DAILYWIRE+

Multiple witnesses have testified that they were afraid of Neely, who entered the train car and allegedly began ranting that someone was going to die that day and that he didn’t care if he went back to jail. These witnesses have all said they feared for their lives, with some even thanking Penny for stepping in, The Daily Wire reported.

In one recording from a police body cam, Alethea Gittings recalled what she heard Neely saying prior to Penny’s intervention.

“I heard the young man that’s on the floor saying, you know, ‘hey, I’m willing to die. You know, I’ll do anything. I’ll go to jail. I don’t care. I don’t care,’” Gittings said.

Gittings testified last Friday that she thanked Penny for his actions.

“The guy in the tan did take him down like, very respectfully and just like held. He just held him. Yeah, yeah, He just held him. He didn’t choke him,” Gittings told officers in the footage played in court.

Penny faces up to 15 years in prison if convicted of manslaughter or up to 4 years if he’s convicted on the lesser charge of criminally negligent homicide.