A former Marine combat instructor testified that Daniel Penny misused a combat maneuver when he fatally choked Jordan Neely aboard a Manhattan subway, saying he appeared to have attempted a “blood choke” and should’ve known to let go after Neely lost consciousness.

Daniel Penny's martial arts instructor from the Marine Corps took the stand Thursday for day six of witness testimony in Penny's trial in the chokehold death of Jordan Neely.

( NewsNation) — In the trial of Daniel Penny, a man accused of killing a homeless and mentally ill man on the New York City subway, jurors are hearing from experts on chokeholds following an admission from a key witness that he lied to police.

The homicide detective who interviewed Daniel Penny shortly after he placed Jordan Neely in a chokehold last year knew that Neely had died, he testified at Penny’s criminal trial Thursday. But Penny, he said, did not. Detective Brian McCarthy said he and his partner interviewed Penny while prosecutors watched secretly behind a one-way mirror.

A former military combat instructor says a fellow Marine veteran misused a combat maneuver when he fatally choked a homeless man aboard a Manhattan subway last year

Done right, the maneuver should knock a person out without killing them, according to a Marines combat instructor who trained Penny. But held too long, the technique can restrict the flow of blood

Penny held Neely in a chokehold for about six minutes — including for more than 50 seconds after Neely stopped moving — according to evidence presented in his criminal trial.

When Daniel Penny fatally choked a homeless man aboard a Manhattan subway last year, the veteran appeared to be using a combat technique that he learned in the Marines, according to a martial arts instructor.