The trial of Daniel Penny, the former Marine charged with killing Jordan Neely aboard a New York City subway, featured testimony from a man who helped the defendant restrain the victim.

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

A Bronx man who helped Daniel Penny restrain Jordan Neely on a New York City subway car last year ”jumped in and tried to help” so Penny could release his chokehold, according to the man’s testimony Wednesday at Penny’s manslaughter and negligent homicide trial.