( NewsNation) — Defense arguments are set to begin Monday in the trial of Daniel Penny, a former Marine accused of killing a mentally ill man on the New York City subway.

Daniel Penny's mother took the stand, along with a forensic pathologist who addressed Jordan Neely's potential mental state. Penny is facing manslaughter charges in the death of Neely on a subway train in 2023.

Prosecutors have had to acknowledge that a victim frightened those around him. The defense lawyers are expected to paint their client as a protector.

Defense attorneys began their defense of a former U.S. Marine charged with fatally choking a homeless man aboard a Manhattan subway by calling the defendant's older sister to the witness stand.

Daniel Penny's sister and childhood friend pleaded his case to jurors at his manslaughter trial — describing the former Marine as a "calm and peaceful" surfing buff who earned a reputation for honesty in their hometown.

Daniel Penny's mother, former Marine sergeants and an airline pilot friend took the witness stand Tuesday in his subway chokehold trial in New York City.

Prosecutors rested their case Monday in the trial of Daniel Penny​, the Marine veteran charged in the chokehold death of Jordan Neely​ on board a subway train last year.

Penny's sister, Jacqueline Penny, and childhood friend, Alexandra Fay, told the jury that the defendant had a reputation for honesty, compassion and empathy among his family and friends in West Islip.