John W. Hinckley Jr., following the advice of his lawyers, told a federal judge yesterday he has "no intention now" of testifying in his own defense at his trial on charges of trying to assassinate President Reagan.

"I have no intention now of taking the stand," Hinckley told Judge Barrington D. Parker while the jury was out of the courtroom. When Parker asked what he meant by "now," Hinckley replied: "Well, I have just been advised by counsel that I have no intention of taking the stand."

Defense lawyer Vincent J. Fuller told Parker during a bench conference that Hinckley had "raised a question about his taking the stand" Tuesday, as the defense neared the end of its case.

Later he told the judge Hinckley had been advised not to testify, adding: "I think he will take our advice."

When Parker asked Hinckley whether he was following his lawyers' advice or making an independent judgment about testifying, Hinckley responded: "I believe both." Hinckley said Fuller had told him he had a constitutional right to testify at his trial.

Chief prosecutor Roger M. Adelman told Parker the government viewed Hinckley's statements yesterday as a waiver of his right to testify at any further stage in the trial.

But Fuller declined to rule out the possibility that the defense might try to call Hinckley as a witness after the prosecution finishes its effort, which began yesterday, to persuade the jury that Hinckley was sane when he shot Reagan and three others.

"I don't know where the government's case is going in the next few weeks, and I think that the most that we can say at this time is we have no present intention of putting any further evidence into this case," Fuller told Parker.

During the last several weeks, the jury has heard extensive testimony from three defense psychiatrists and a psychologist. All four said they believe Hinckley suffered from mental illness when he shot Reagan and should not be held criminally responsible for his acts.

The final defense testimony yesterday came from Dr. Daniel R. Weinberger, a psychiatrist at the National Institute of Mental Health. He told the jury that abnormalities revealed by sophisticated X-rays of Hinckley's brain were more likely to be found in schizophrenics than in normal persons. Weinberger testified, however, that not all persons who have such abnormalities are schizophrenic.

Prosecutor Adelman began his case with testimony from former deputy D.C. medical examiner William J. Brownlee, who examined Hinckley the night of the shooting, and from D.C. police detective Arthur E. Myers, a homicide investigator. Myers met Hinckley in the police cellblock 20 minutes after the incident and remained with him for about eight hours.

Brownlee, a medical doctor who examined Hinckley for 25 minutes five hours after the shooting, testified that Hinckley "did not appear abnormal to me at all."

Except for appearing "somewhat fidgety," Brownlee said, Hinckley "showed no unusual reaction, taking into consideration the gravity of the situation at that particular time." Brownlee said Hinckley "seemed much calmer to me" after he spoke with his father by telephone.

Brownlee said Hinckley was "slightly withdrawn but not depressed at all . . . ." He testified that he thought Hinckley's responses during the examination were appropriate except for a "slight degree of anxiety."

Brownlee said Hinckley told him he had taken his normal dosage of an allergy drug on the morning of the shooting. Hinckley also said he had been taking the tranquilizer Valium for about nine months but did not say he had taken any of that drug that day, Brownlee said.

A defense psychiatrist, Dr. David Michael Bear, had testified earlier in the trial that Hinckley told him that he took an extra dose of Valium three hours before the shooting. Bear told the jury that the extra Valium may have helped trigger Hinckley's attack on Reagan.

Brownlee told the jury that after he examined Hinckley at the FBI's Washington Field Office, he ordered a prescription of Valium for him because Hinckley had a history of using it and because he didn't want Hinckley to experience "withdrawal" symptoms. Brownlee said he also ordered some of the allergy drug for Hinckley.

During his examination of Hinckley, Brownlee told the jury, he noticed healed scars, which appeared to be about a year old, on the inside of both of Hinckley's wrists. Brownlee testified that as a result of that finding, he advised the FBI to take all precautions to avoid any suicide attempt by Hinckley.

Defense psychiatrists repeatedly testified that Hinckley was suffering from schizophrenia, a severe break with reality, but that the nature of his illness was such that he would appear calm and responsive to an observer. Brownlee testified yesterday that he was aware that at times psychotic persons do appear to be in touch with reality.

When questioned by Fuller, Brownlee also testified that he had not asked Hinckley whether he had a history of depression or had received psychiatric treatment. According to defense testimony, Hinckley had been treated by a Colorado psychiatrist for five months prior to the shooting.

Detective Myers testified that Hinckley was "totally in control of himself," was polite and cooperative and even spelled the word "assassinate" for him as Myers was filling out a report. When Myers was asked to point Hinckley out in the courtroom, Hinckley waved.

Myers testified that while Hinckley was in custody, he asked about the status of a collegiate basketball championship on television, expressed concern about his safety in police headquarters and "sort of laughed" when Myers quipped to him: "You must be a Democrat."

Under cross-examination, Myers agreed with Fuller's description that Hinckley appeared "like he was glad it was over." Myers added: "It appeared to me that he was relieved that he had shot the president."

Myers, who will continue his testimony today, also acknowledged that when he asked Hinckley, "Why did you do this?" Hinckley told him to look in his hotel room and "you'll know why." In that room, officials found an unmailed letter to actress Jodie Foster in which Hinckley wrote that he hoped by "this historical deed to gain your respect and love."