Virginia cannot reinstate the death sentence of a Northern Virginia man convicted of killing a Lynchburg couple, the U.S. Supreme Court ruled Monday.

The state's attorney general's office fought to keep Leon Winston, 31, on death row for the shooting deaths of Anthony and Rhonda Robinson at their home in 2002. Rhonda, who was pregnant, was shot in front of her 4- and 8-year-old daughters.

The case returns to the state court for resentencing.

A Virginia appeals court threw out the death sentence last year after defense attorneys found that Fairfax County Public Schools determined that Winston had an IQ that showed he was mentally retarded.

The Supreme Court ruled in 2002 that executing the mentally retarded was cruel and unusual punishment and unconstitutional.

The state argued that Winston waited too late to produce evidence that he was mentally retarded.