Two African-American half-brothers who spent 31 years in prison in the southern US state of North Carolina for a crime they did not commit have been awarded $84 million, their lawyer said Monday.

"This is the largest jury verdict ever returned in a wrongful conviction case in the history of the United States," Des Hogan told AFP.

Henry Lee McCollum and his half-brother Leon Brown, both of whom are intellectually disabled, were convicted of the 1983 rape and murder of an 11-year-old girl.

They were respectively 19 and 15 years old at the time of their arrest and claimed to have been forced to sign confessions.

Crime scene police line | Representational Image
Crime scene police line | Representational Image GETTY IMAGES / SCOTT OLSON

Their convictions were overturned in 2014 after the discovery of DNA evidence that placed another man at the scene where the girl's body was found.

McCollum and Brown pursued a federal civil rights case and a jury on Friday awarded them a total of $84 million in compensatory damages, punitive damages and interest.

"The jury sent a message that the old times of ignoring the rights of the poor, the people of color, the marginalised in rural counties, are gone," Hogan said.

"They are thrilled that they won, they are happy that the jury said the sheriff was wrong," Hogan said. "They were vindicated."