A former Prince George's County fireman, accused of killing a 13-year-old girl last August, asked a Circuit Court yesterday to declare his statement to police about the incident inadmissible as evidence at his trial.

The suspect, William Joseph Parker, 27, told Judge Howard S. Chasanow he had been insufficiently advised of his rights to have a lawyer and of his rights to remain silent when he gave a written and signed statement to Prince George's detectives early on the morning of Sept. 15.

According to testimony at the two-day hearing, Parker had been advised of his rights to counsel and silence when first brought in for questioning at the county's Bureau of Criminal In vestigation on the afternoon of Sept. 14. Parker admitted he signed a paper waiving those rights.

But Parker's lawyer, Fred W. Bennett, said Parker was entitled to be readvised of his rights each time a new police officer began questioning him about the event.

Parker was questioned for a total of nine hours, first by Cpl. Earl W. Jones, then by Cpl. T. R. Tucker and finally by Det. Wallace Sibila before making the statement to Sibila in which, according to Jones, "he confessed" to the killing.

Although he testified he was not beaten or otherwise physically mistreated, Parker said he had been fighting fires the previous night with the Kentland Volunteer Fire Department, had only had one hour's sleep and was tired and not fully alert while being questioned.

Parker is accused in the Aug. 28 murder of Elizabeth Archard of Annapolis, whose body was found in a wooded area near Bowie the next day. Tests showed she had been raped, then shot five times in the neck.

Parker said that while being questioned by both Tucker and Sibila, he did ask for a lawyer, but the policemen denied this.

His lawyer, Bennett, said Parker was beaten by three fellow inmates at the Prince George's detention center after Thursday's hearing and he asked for special protective measures. "They have access to radio and television and they heard things they didn't like," Bennett said.

The hearing was recessed until Tuesday after prosecutor Edmond B. O'Connell, suffering from a severe cold, lost his voice.