Despite CPR being performed on the teen, she was declared dead later at hospital.
Watkins was found guilty of murder instead of voluntary manslaughter, as his 13-year-old brother tried to get him to stop choking their sister.
Bibb County Superior Judge Verda Colvin said, ‘In those ten minutes, she had to have stopped moving. Perhaps that wasn’t noticed bu the defendant because he was still angry.’
Watkins and his family cried in court when the sentence was announced.
Ms Colvin said ‘I think everyone understands’ and said she was sorry adults in his life had let him down and never disciplained him or gave him the tools to deal with his anger.
‘In this household, chaos was empowered,’ she said, ‘the ability to ignore and follow corrective discipline was empowered.’
Through tears, Watkins said ‘I’m sorry,’ before being led out of the courtroom.