A South Carolina man who blamed the antidepressant drug Zoloft in the shotgun slayings of his grandparents when he was 12 years old has pleaded guilty to voluntary manslaughter.

Christopher Pittman accepted a plea deal Thursday that shortens the prison sentence he was handed after a previous trial.

The now-21-year-old man earned a new trial when a judge in July ruled Pittman's original attorneys didn't pursue a plea deal and focused too much on Zoloft during his 2005 trial.

Thursday's plea means Pittman could be released from prison in about 12 years.

He had been serving a 30-year term after being convicted as an adult on two counts of murder in the 2001 shooting of his grandparents in their Chester home.