A soldier being court-martialed on a U.S. Army base near Seattle for the murder of three Afghan civilians has agreed to plead guilty Wednesday in hopes of earning a reduced sentence, according to one of the attorneys handling his case.

"My client is admitting on the record to three counts of murder, plus one count of conspiracy to commit assault and battery and one count of illegal drug use," said Geoffrey Nathan, a lawyer for Army Spc. Jeremy Morlock.

This...