A former US Marine instructor who abused Muslim military recruits - including ordering them into an industrial clothes dryer and turning it on - will be sentenced to prison on Friday.

Gunnery Sergeant Joseph Felix, 34, was found guilty of "maltreatment" on Thursday after he physically and verbally abused three American Muslims training to become US Marines at a facility in Parris Island in South Carolina state.

Felix "picked out Muslim recruits for special abuse because of their Muslim faith. He degraded their religion and put them in industrial appliances", Lieutenant-Colonel John Norman, the prosecutor, was quoted as saying by the Washington Post.

Witnesses said they heard Felix use the terms "terrorist" and "ISIS" when addressing the Muslim men.

A $100m civil lawsuit has also been filed against the Marine Corps and the American government by the family of one Muslim man who fell 12 metres to his death.

Defence lawyers said it was a suicide, while the family of Raheel Siddiqui allege the abuse he suffered led to him jumping.

Felix was also convicted of violating general orders, drunk and disorderly conduct, and making false statements.

Recruits Ameer Bourmeche and ­Rekan Hawez testified they were ordered into an industrial clothes dryer.

Navy Lieutenant Commander Daniel Bridges, a defence lawyer, argued Felix did not know the three men were Muslim.

Twenty Marine instructors, officers, and staff members have been investigated over allegations they abused Muslim recruits since 2015 with 13 facing punishment, the Post reported.