A judge has refused to bail four people accused of beating a mentally-disabled man and broadcasting the attack on Facebook Live.

The footage showed a woman laughing and smoking as others used a knife to tear the victim's clothes and cut his hair until his scalp bled.

He was bound, gagged, beaten and stabbed with a knife before the group shouted obscenities about President-elect Donald Trump and "white people".

During the attack, one of the accused - Jordan Hill - contacted the victim's mother and demanded $300 in exchange for her son, according to prosecutors.

Hill, 18, is accused alongside Brittany Covington, 18, Tesfaye Cooper, 18, and Tanishia Covington, 24.

The four African-Americans face aggravated kidnapping charges and hate crime charges, due to the victim's race and mental disabilities. They have also been charged with aggravated unlawful restraint and aggravated battery with a deadly weapon.

On Friday they appeared before Cook County Circuit Judge Maria Kuriakos Ciesil, who ordered they be kept in custody, telling them they were "a danger" to society.

Defence lawyers described the four as hardworking, responsible and religious.

However, the judge responded "I'm looking at each of you and wondering where was the sense of decency that each of you should have had? I don't see it."

The Covington sisters, Hill and Cooper will next appear in court on 27 January.