'The Green Mile' movie by Stephen King was inspired by this case.
________
This is George Stinney Jr he was falsely convicted and murdered by the U.S at only 14. He was accused of killing two white girls, Betty of 11-years-old and Mary of 7, the bodies were found near the house where the boy resided with his parents. 

Before the execution, George spent 81 days in prison without being able to see his parents, he was held in solitary 80 miles from the city, he was held alone without anybody to talk to. 

He was heard alone without the presence of his parents or a lawyer. At that time, all the jurors were white. The trial lasted only 2 hours and the sentence was handed down 10 minutes later. The boy's parents were not allowed in the court room, and was subsequently expelled from that city after the trial. 

During his trial, until the day of his execution, he always carried a Bible in his hands, claiming for innocence. 

He was too short for the electric chair so they used the Bible he was carrying as a booster seat. He was electrocuted with 5,380 volts in the head. 

70 years later, his innocence was finally proven by a judge in South Carolina. The beam with which the two girls were killed, weighed more than 19.07 kilograms.

Therefore, it was impossible for Stinney to be able to lift it, let alone be able to hit hard enough to kill them.