The attorney for Randolph Alan Gaul, accused in the 1978 slaying of a 13-year-old Hyattsville, girl, yesterday accused the Prince George's County prosecutor of withholding information crucial to Gaul's defense.

Circuit Court Judge Jacob S. Levin then ordered the prosecutor to turn over to the defense information regarding alleged confessions to the crime made by three different persons, which police, accustomed to having "confessors" take credit for crimes they did not commit, had discounted.

Gual was charged with murdering Kathy Murphy last June after he gave a signed statement to detectives describing his tortured emotions in a chance meeting with the young girl. His trial was scheduled to begin today, but his attorney, James Kenkel, asked for a postponement after yesterday's preliminary proceedings because of the new information about the previous confessions. Levin is scheduled to rule on his request today.

In Levin's courtroom yesterday, a deputy state's attorney, Joseph Sauerwein, agreed to turn over the names of the three previous alleged confessors to Kenkel after an angry exchange and an hour-long closed-door conference.

Sauerwein had insisted that he did not turn over the information previously because the confessions were "inconsistent with the facts of the case." He also said that the information "should not be any surprise" to Kenkel because it had appeared last week in a story in The Washington Post. k

Sauerwein also agreed to turn over other information -- including a tape recording of an interview of Gaul by the arresting officer -- that Kenkel demanded yesterday.

The case of Kathy Murphy had baffled police for two years after the girl's nude body was found lying face down in Sligo Creek in her West Hyattsville neighborhood.