A 22-year-old commercial fisherman is scheduled to be arraigned today on a charge of murdering his 3 1/2-month-old nephew in Annandale, Fairfax County police said yesterday.

Thomas S. Jenkins was charged in the Saturday night slaying of Jonathan O. Dyer, the infant son of Bruce and Diane Dyer of 7814 Thor Dr. Jenkins is Diane Dyer's brother and recently lived at the Dyers' home, police said. He was held without bond yesterday at the county jail.

The Dyers and two other children were at home when the 7 p.m. incident occurred, police said. "Noises were heard by other family members and the little boy was found by an older brother lying on the floor," said police spokesman Warren R. Carmichael. The infant was taken by his father to Fairfax Hospital, where he was pronounced dead.

Carmichael said the child had suffered massive internal injuries and appeared to have been severely struck or thrown. An autopsy had not yet been performed yesterday, Carmichael noted, adding that police are still investigating the death. No motive had yet been established for the incident, Carmichael said.

Several neighbors said the Dyers had recently moved to the quiet residential community. Carmichael said the investigation so far had turned up "no indication" that any weapon was used in the slaying or that alcohol or drugs played any role in the incident. Investigators have found "no obvious motive," Carmichael added.