A psychiatrist for the prosecution yesterday portrayed John W. Hinckley Jr. as a manipulative young man who repeatedly lied to obtain money and sympathy from his family and even made up a girlfriend--"Lynn Collins"--to "get his parents off his back."

Dr. Park Elliott Dietz told the jury that in the months before Hinckley shot President Reagan, Hinckley complained that he had not received his inheritance from the family oil and gas business and used physical illnesses, like weakness in his legs, as excuses to avoid working for a living.

Dietz testified that in the meantime Hinckley, who had pursued a rock music career in Hollywood and later began writing poetry and stories, had developed a strong desire to achieve fame without effort.

"Mr. Hinckley has a longstanding interest in becoming famous without working," Dietz told the jury yesterday, as Hinckley's trial moved into the sixth week of testimony in U.S. District Court.

The psychiatrist said that Hinckley's manipulative actions included creating a fictitious girlfriend, whom he called "Lynn Collins" in letters he wrote to his parents beginning in 1976. He described a warm relationship with her and frequently cited this relationship when appealing to his parents for money to stay in California.

Dietz said that Hinckley's physical complaints, which doctors attributed to anxiety, heightened in early 1980 when he began to buy guns and consider what kind of "high-publicity crime" he would commit to achieve the fame he sought.

Dietz, an assistant professor of psychiatry at the Harvard Medical School who interviewed Hinckley for 25 hours after the shooting, testified last week that Hinckley suffered from a mood disturbance and personality disorders.

But, he said, Hinckley nevertheless was in control of his behavior when he wounded Reagan and three others outside the Washington Hilton Hotel on March 30, 1981.

During testimony yesterday, Dietz refuted the opinions of defense psychiatrists who have told the jury that Hinckley was driven by suicidal impulses and by a belief that his acts would lead to an eternal union with the unattainable object of his obsession, actress Jodie Foster.

Yesterday, Dietz quoted Hinckley as telling prosecution psychiatrists in interviews shortly after the shooting, "I wasn't that desperate to act." At one point, Dietz recalled Hinckley saying, Hinckley considered abandoning the plan because of the rainy weather the afternoon of the attack.

The jury has already been told that Hinckley told a doctor that the thought "Should I? Should I?" went through his mind repeatedly as he stood outside the hotel.

Dietz testified yesterday that these statements showed that Hinckley "deliberated about the moral quality of the act intended."

In addition, Dietz testified yesterday, the fact that Hinckley had 43 bullets in his hotel room that day and loaded his gun with the six most lethal ones--exploding or "Devastator" bullets--showed Hinckley was capable of deliberate, organized conduct.

"It shows that he was not driven by wild emotional forces carrying him hither and yon but rather that he was carrying out specific planned behavior," Dietz testified.

The key to the government's assertion that Hinckley was not legally insane at the time of the shooting is the contention that he knew the wrongfulness of the act and was capable of abiding by the law if he desired.

Dietz testified yesterday that an unmailed letter that Hinckley left in his hotel room before the shooting, in which Hinckley admits he might be killed "in my attempt to get Reagan," shows that Hinckley was aware of his decision to act and knew that law enforcement officials would try to stop him because the act was wrong.

"A man driven by passion, by uncontrollable forces is not often inclined to write a letter and explain what it is all about," Dietz added under questioning by chief government prosecutor Roger M. Adelman. "He Hinckley did."

Dietz also disputed claims by defense psychiatrists that Reagan emerged from the Hilton so quickly that Hinckley didn't have time to think about what he might be doing and back out, as he had when he stalked President Carter and Reagan in earlier months and not fired a shot.

Dietz said Hinckley saw Reagan enter the hotel, waited around for the president to leave and thus had time to deliberate.

"A man driven, a man out of control would not have the capacity to wait at that moment for the best shot," Dietz testified.

Hinckley said after the shooting that he expected to be "blasted" by U.S. Secret Service agents after he fired on Reagan. This indicated, Dietz said yesterday, that Hinckley knew his act was wrong and also refuted ideas that the attack was a suicidal gesture.

Dietz contended that Hinckley positioned himself in a crowd of innocent bystanders and thereby virtually ruled out any shots from the Secret Service. If Hinckley were intent on suicide, Dietz testified, he could have shot himself in his third floor hotel room or jumped out the window.

Dietz said it was "perfectly normal" for Hinckley to imitate characters and plots in movies and books, including the main character in the movie "Taxi Driver." Hinckley chose to imitate crimes, Dietz said, because he wanted to be famous.

Dietz said that Hinckley told him that when he shot Reagan he hoped not only to impress but to "almost traumatize" actress Foster. Hinckley said he was angry that Foster had rejected him but also "willing to sacrifice a great deal" to express his love to her, Dietz recalled.

Dietz said Hinckley told him, "Actually, I should feel good. I accomplished everything on a grand scale."