Atlanta, January 28 (RHC)-- An African American prisoner has been executed in the United States despite being mentally disabled, according to his lawyers. Warren Lee Hill was put to death by injection of a single drug at a prison in Jackson, Georgia, on Tuesday.

The 54-year-old, convicted of killing a fellow inmate, was pronounced dead at 7:55 pm local time. The execution came despite last-minute efforts by Hill's lawyers to get the U.S. Supreme Court to prevent the move, against which temporary reprieves had been granted by different courts on three previous occasions.

Hill's lawyers have long argued that the man, initially given life terms for killing his girlfriend, has been intellectually disabled throughout his life. In an e-mail statement prior to the execution, Brian Kammer, a lawyer for Hill, said: "The clemency board missed an opportunity to right a grave wrong," and "it is now up to the U.S. Supreme Court to ensure that an unconstitutional execution of a man with lifelong intellectual disability is prevented." But the Supreme Court denied the allegations and refused to halt the execution.

According to the American Civil Liberties Union (ACLU), the racial ratio of the victims of the death penalty in the U.S. has been striking since the revival of the practice in 1976, with the penalty being disproportionately imposed on Blacks and ethnic minorities.