The 12 jurors deciding John W. Hinckley Jr.'s fate failed to reach a verdict after eight hours of deliberation yesterday.

U.S. District Judge Barrington D. Parker excused the jurors shortly before 6. They will return to the courthouse at 10 a.m. today to take up again the question of whether Hinckley was legally insane when he shot President Reagan and three other persons outside the Washington Hilton Hotel more than a year ago.

The jurors sent four notes to Parker yesterday, asking for extra writing supplies, a dictionary, a list of the exhibits introduced into evidence and transcripts of testimony from several of the 40 witnesses who appeared at Hinckley's trial.

After meeting in his chambers with prosecution and defense lawyers, Parker denied the jury's request for the dictionary and the testimony from the witnesses. A statement from the court describing the notes did not say whose testimony was sought. Customarily, judges turn down such requests because jurors are supposed to rely on their own recollection of the evidence and not transcripts or dictionary definitions.

In one of the notes, the jury of seven women and five men identified its foreman as Roy Jackson, 64, of Northwest Washington.

The jury's deliberations, which began Friday afternoon, now total 11 1/2 hours.

The jurors are working in the same wood-paneled courtroom where they sat for more than six weeks listening to a small parade of psychiatrists testify about Hinckley's mental condition on March 30, 1981, when he shot President Reagan and three others.

The sixth-floor hallway in the vicinity of that courtroom was cordoned off yesterday, and the windows in the door to the courtroom were covered with paper. Reporters, artists and a few spectators were camped out nearby, eating, reading, playing cards and even sleeping on the stone floor. The only activity of note occurred when the jury filed in and out for lunch.

Hinckley's parents and his older brother Scott arrived at the courthouse at 1:30 p.m. The family visited Hinckley in the basement cellblock where he has been housed during his trial and now awaits the jury's verdict on his claim that he was legally insane when he attacked the president.

The Hinckleys spent most of the afternoon waiting in a second-floor witness room. John W. Hinckley Sr. occasionally spoke to his son's defense lawyers, who were on call in the courthouse along with the prosecution team. From time to time he paced up and down the second floor hallway, his hands clasped behind his back.

Meanwhile yesterday, Parker, granting a request from lawyers for The New York Times, released a list of the names and addresses of the jurors, as well as the six alternate jurors, all of whom are sequestered during the course of deliberations.

Parker issued a brief order saying he found the newspaper's arguments for release to be "compelling and persuasive." Parker also noted since the jury is sequestered, release of their names would not "influence their deliberations in any way."