A Montgomery County Circuit Court judge refused yesterday to release a 10-year-old Ethiopian boy from a juvenile detention center where the youth has been held since July awaiting a hearing on charges that he beat a 7-year-old playmate.

Circuit Court Judge Richard B. Latham turned down a plea for the youth's release after a psychologist testified at a hearing that the youth had engaged in two violent outbursts against staff members and had a history of running away from home.

"It's obvious to the court that this young man, when he has been involved in stressful situations, has run away," said Latham. Coupled with the outbursts, Latham said there was a "strong probability" that the youth would run away again, which would "not be in his best interests."

The youth's lawyer, Arthur G. House, argued that the boy is being held "without probable cause" and had been harassed and assaulted at least once by other inmates at the center.

"I think he's acting out the way most 10-year-olds would act out if they suddenly got put in prison," House said.

At the time of the incident, the boy, whose name is being withheld because he is a juvenile, ran for help and later described in vivid detail how two teen-agers had attacked his friend in a wooded area in their Aspen Hill neighborhood.

For several days, a well-publicized investigation by county police focused on the alleged suspects, but the boy was ultimately charged with assault and filing a false crime report.

The youth was sent to the Noyes Children Center in Rockville immediately after his arrest on July 23 and has been held for evaluation ever since.

Yesterday, House said evidence will show that the incident was the result of an accidental injury. "There was nothing done maliciously to this child at all," House said.