( 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.

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.

A subway commuter who helped an ex-Marine restrain an agitated man aboard a Manhattan subway last year testified that he tried to convince the veteran to loosen his grip around the man’s neck.