Arthur Alston, the ringleader of a group of teenage boys convicted of the fatal beating of a man on a Center City subway platform, was sentenced to 12-and-a-half to 25 years in prison this afternoon.

Alston, 18, wiped tears from his eyes as Judge Jeffrey Minehart gave him 10 to 20 years for the third-degree March 2008 murder of Sean Patrick Conroy, and 2 and a half to five years for assaulting a student at school while he was on house arrest after the murder.

"I'm not a murderer. I'm not a monster. I'm a kid who made a mistake," said Alston, who was 16 at the time of the attack.

Three of Alston's co-defendants were previously sentenced by Minehart to 12-and-a-half to 25 years in prison, while a fifth co-defendant will be sentenced Jan. 4.

Conroy, 36, died of an asthma attack triggered by the beating, which the boys engaged in after daring each other to attack a stranger.