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.

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

( 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.