Montgomery County police charged a 42-year-old man yesterday with first-degree murder in the death of his 75-year-old mother, whose decomposing body was found Saturday in the living room of her Wheaton house.

Walter Marquez, who has no permanent address, is accused of beating Esperanza Marquez to death with a tree limb. It was found near the front door of the house, said Officer Derek Baliles, a department spokesman.

The woman lived alone in the 4000 block of Ferrara Drive in Veirs Mill Village. A preliminary examination revealed that she died of blows to the head, Baliles said. The body was in early stages of decomposition, he said.

Police arrested Walter Marquez at Washington Adventist Hospital in Takoma Park about 12:30 a.m., after hospital staff alerted them to his presence. He was being held yesterday without bail at Montgomery County Detention Center.

The defendant's brother called police Saturday afternoon after finding the body. Walter Marquez was seated on a couch nearby watching television, the brother told investigators.