WASHINGTON (AP) _ For the second time in three years, the Supreme Court today threw out the murder conviction of a South Carolina man because of the instructions given the jury at his trial.

Dale Robert Yates, on death row since 1981, is now entitled to a new trial. He had been convicted of killing a woman during a country story robbery.

The high court ruled unanimously that the South Carolina Supreme Court ''employed a deficient standard of review'' when it found that faulty instructions given the jury were a harmless error.

''The ... jury instructions found to have been erroneous in this case may not be excused as harmless error,'' Justice David H. Souter wrote for the court.

In 1988, the high court threw out Yates' murder conviction because jurors had been told they could conclude that he meant to hurt someone because he was carrying a gun when the robbery occurred.

Yates actually killed no one. His accomplice, Henry Davis, fatally stabbed a woman during the robbery before being fatally shot by the store owner.

After the 1988 ruling, Yates' case returned to the state Supreme Court. It reinstated the murder conviction after finding that the faulty jury instruction had been harmless - that Yates would have been convicted anyway.

Yates had been convicted in the fatal stabbing of Helen Wood, 68, during the robbery of her son's Greenville County store Feb. 13, 1981.

He had entered the store armed with a gun. Davis was carrying a knife.

After shooting and wounding Mrs. Wood's son, Yates fled the store. Davis then killed Mrs. Woods before being fatally shot by her son.

After reviewing Supreme Court rulings that bar jurors from being told they can presume a defendant intended the ordinary consequences of his actions, Souter said jurors at Yates' trial wrongly were told what they could presume about his carrying a gun.

Souter added that the state Supreme Court had ''failed to apply the proper harmless-error standard ... in this case.''

The case is Yates vs. Evatt, 89-7691.