A St. Mary's County jury reported tonight it was deadlocked in the case of William Joseph Parker, accused of abducting, raping and murdering a 13-year-old girl in Prince George's County. The jurors were dismissed for the night and told to resume negotiations Saturday morning.

The jury had deliberated for about 9 1/2 hours before being sent to a motel by Circuit Judge Howard S. Chasanow shortly after 11 p.m.

Parker, a 28-year-old volunteer fireman, could be sentenced to die in Maryland's gas chamber if convicted in the slaying of Elizabeth C. Archard last Aug. 28. He would be the first person to receive a death sentence in the nine months that the state's new capital punishment law has been in effect.

The jury began deliberating this afternoon after receiving instructions from the judge and hearing lengthy closing arguments. The trial, in its fifth day, was moved here from Prince George's County because of pretrial publicity.

The prosecution charged that Parker met Archard on her bicycle about a mile from her Annapolis home, took her in his car to a wooded area of Bowie, then raped her and shot her fvie times.

If Parker is found guilty of first-degree murder he would be subject to the death penalty if he is also found guilty of either first-degree rape or adbuction.

Parker's attorney, Fred W. Bennett, has argued throughout the trial that police had violated Parker's constitutional rights. He also argued that Parker is innocent of first-degree murder.

In his closing arguments today, prosecutor Edmond B. O'Connell said, "Elizabeth Archard began Aug. 28 like any normal 13-year-old girl, not knowing that it was going to be the last day of her life."

From there, O'Connell launched into a chronology of the evidence, leading up to Archard's encounter with Parker at a recreation area called the pony ring. "At that point," O'Connell said, "Elizabeth Archard had the misfortune to meet Mr. Parker, a man with personal problems a man with a quick temper."

O'Connell theorized that Parker, contrary to a statement he made to police, forced Archard into his carm tossing her bicycle behind a nearby hedge, then drove her, against her will, to the wooded area where her body was found.

Paker said in that statement that he drove Archard to the wooded area and had sex with her. Then, when Archard said, "i'm going to tell my father," Parker said he "blacked out" and recovered to find himself standing over Archard with gun in hand.

"She told him she was going to tell her father," O'Connell recounted. "He knew he was in trouble and had to do something about it. So he went back to his car, went under the seat, got the gun out and killed Elizabeth Archard."

Bennett spent much of his 95-minute closing argument concentrating on the methods used by Prince George's County police detectives on the night of Sept. 14, when Parker made his statement.

"Mr. O'Connell was long on the facts in this case but woefully short on telling you the law, the law on how you will decide whether Mr. Parker's statement was voluntary or not," Bennett declared.

Bennett then cited, in detail, cases in which statements made by the defense had been thrown out by presiding judges because the defendant's rights had been violated. He maintained that when police switched interrogators, they had a responsibility to advise Parker of his rights a second time.

Judge Chasanow had ruled Parker's statement admissible as evidence at his trial.

"After detective (Tony R.) Tucker said to Mr. Parker, 'It would be better if you talked. They have the evidence on you,' he lost the right to take a statement from him," Bennett said. "And when Mr. Parker asked for a lawyer-as Parker testified yesterday that he did-the police had the obligation to stop questioning him. But they did not."

Bennett noted that credibility was a crucial issue because the three police detectives who questioned Parker testified that he never asked for a lawyer.

Bennett then maintained that even if the jury found the statement voluntary, "this was still a classic case of second-degree murder or manslaughter, not first-degree murder, which is defined as killing with malice and premeditation.

"Mr. Parker snapped, he lost his cool, he is going to pay the price if you find his statement voluntary."

Bennett also said that there was no evidence to contradict Parker's statement that Archard voluntarily got into his car and voluntarily had sex with him.

In a brief rebuttal, O'Connell said, "Do you, (the jury) believe that a 13-year-old girl who had been told on a number of occasions not to get into a car with strangers would get into a car with him?" As he spoke the final words of the sentence, the prosecutor whirled and pointed at Parker, who sat staring at him from the defense table.