A federal judge has thrown out the death sentence for a man who stabbed his grandparents to death in their St. Louis-area home in 1996.

U.S. District Judge E. Richard Webber's 189-page ruling benefiting 39-year-old David Barnett ordered the state to sentence Barnett to life in prison without parole or to decide within 180 days whether to pursue another death sentence during a new hearing.

Barnett killed Clifford Barnett and Leona Barnett after they returned from a post-church brunch.

He confessed to police the next day, and jurors later convicted him of first-degree murder.

Webber ruled that Barnett's trial attorneys didn't adequately investigate and present mitigating evidence relating to Barnett's dysfunctional background.

A spokeswoman for Missouri Attorney General Chris Koster says that office is reviewing Webber's ruling.

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