A U.S. District judge, reversing an earlier decision, said yesterday he will allow jurors in the trial of John W. Hinckley Jr., accused of attempting to assassinate President Reagan, to return to their homes after each day's court session instead of sequestering them in a local hotel.

Both the Justice Department and the U.S. Attorney's office had wanted Parker to sequester the jury, in the custody of the U.S. Marshal Service, primarily to shield them from the widespread publicity that is expected to surround the case. The trial, which could take as long as a month to complete, is scheduled to begin April 27.

Parker, in deciding to let the jurors go home each night, said he was concerned about the "frayed nerves" that jury members often suffer when they are sequestered away from their homes and families.

Hinckley, who is in custody in Fort Meade, Md., has admitted that he fired the shots from a .22-caliber pistol that wounded Reagan, his press secretary, a D.C. police officer and a U.S. Secret Service agent outside the Washington Hilton Hotel a year ago. But Hinckley argues that he was insane at the time of the incident and thus should not be held criminally responsible for his acts.

One of Hinckley's defense lawyers said in court yesterday that the defense believes that the prosecution will present testimony during the trial from all four victims in the case. The government has refused to say whether Reagan will testify at the trial, or whether he will give sworn testimony through a written or videotaped deposition.

Last December, when it was expected that Hinckley's trial would start in January, Parker ruled that the jury would be sequestered. Yesterday, Parker vacated that order. During hearings in the past few months, while pretrial evidentiary questions were decided by the federal appeals court, Parker had indicated that he was reconsidering the sequestration issue.

Juries are routinely sequestered in the federal court here in cases that attract much publicity, with the decision left up to the discretion of the presiding judge.

Assistant U.S. Attorney Roger M. Adelman told Parker during a hearing yesterday that the jurors themselves will be "celebrities of sort" during the trial and might be approached by relatives or others interested in the case.

The government's principal concern is that during the trial, the jurors might inadvertently see media reports about the case or be subject to other outside influences that could sway their ultimate decision.

Parker, however, expressed his concern about what he called "frayed nerves" that develop among jurors when they are sequestered and their activities strictly limited during a long trial. When a jury is sequestered, telephone calls and reading material are monitored by deputy marshals, who also oversee meals and activities when court is not in session.

Hinckley's defense lawyers have consistently argued against a sequestration order in the case. Yesterday, defense lawyer Vincent Fuller told Parker that he was sure the jurors could abide by court directives that they not read or listen to media reports about the case and not discuss the matter with anyone until after they have rendered their verdict.

In other developments at yesterday's hearing, Parker rejected a defense request that Hinckley's trial be split into two parts, with two juries. The defense wanted one jury to decide whether Hinckley committed the crime and the second to consider the question of his sanity.

Gregory Craig, another Hinckley defense lawyer, argued yesterday that the case should be split so that the jury that decides the question of Hinckley's sanity would be isolated from the "emotion-laden" evidence presented by the government about the facts of the crime, which could include television footage of the shooting incident.

In denying the request, Parker cited what he described as the "drain" on court resources and human endurance, for lawyers, jurors, and Hinckley himself, if two juries were empaneled to hear the case.

During yesterday's hearing, it was also disclosed that psychiatric experts for both the prosecution and defense have viewed the movie "Taxi Driver" and will refer to that film during their testimony about Hinckley's mental state.

In the film, a deranged taxi driver attempts to assassinate a presidential candidate to impress a young prostitute, played by the actress Jodie Foster. Sources have said that Hinckley had seen the movie, and a letter confiscated from his hotel room after he shot Reagan indicates he carried out the assassination attempt to gain Foster's attention. The defense has said it wants to show the movie to the jury.