Many Washingtonians expressed surprise and, in some cases, cynicism last night when they learned that a federal jury had found John W. Hinckley Jr. not guilty because he was legally insane.

But spokesmen for President Reagan and two of the three other men who were wounded during Hinckley's March 30, 1981, attack declined to comment on the verdict.

A White House spokesman said there would be no comment from the president. Mrs. Sarah Brady, wife of White House press secretary James Brady, said, "My husband and I have decided not to say anything." A woman who answered the telephone at the home of D.C. police officer Tom Delahanty said he was not available to comment.

The fourth man who was wounded, Secret Service agent Tim McCarthy, could not be reached for comment.

Secret Service spokesman Mary Ann Gordon also declined to characterize the jury's verdict. "We feel that it's not in the best interest of the judicial process to make any statements," she said.

But when a reporter conveyed the news to 13 people in and around the Metro Center subway station last night, the common reactions were double takes, exclamations and eye rolling. Everyone was aware of the trial. Only two of the 13 expressed no opinion about the verdict; no one supported it.

"Holy Mackerel! On all counts? I just think it's pretty incredible," said David Spiegel, an accountant. "Hard to swallow, man, hard to swallow," said station attendant T. Brunson.

"Baloney!" said a taxi driver who gave his name as John Anderson and said he was from Nigeria. " The American system of justice is stupid. You mean Hinckley can't take responsibility for his action and people who are sane would find him not guilty? Outrageous! I just can't believe it."

Some people cast the verdict as the outcome of the wealth of Hinckley's father, who is chairman of the board of a Colorado oil and gas exploration company.

Accountant Spiegel said that Hinckley was able to have the best lawyers. "I'm sure some poor guy off the street wouldn't be able to get all that expert testimony," he said.

Some black people interviewed expressed the opinion that Hinckley would have met a different fate had he not been white, despite the fact that the jury consisted of 11 blacks and one white. "He would have got locked up," said Gloria Parker, a data processor. " . . . I still say the man's not crazy."

Others saw Hinckley's successful insanity defense as a corruption of the judicial system.

Station attendant Brunson saw the verdict as an invitation to crime without punishment. People now will think, " 'I can go run my car into IBM, shoot up some people and I can just say I'm insane,' " he said, referring to the shooting spree in Bethesda in which three people were killed.

U.S. Transportation Department official Norbert Zucker viewed the verdict as "another instance of where the criminal is given a lot more consideration by the judicial system than the victims."

"What are they defining as insanity these days?" asked Maryland student Yasmine Khan. "Anybody seems to be able to get away with anything these days."

In Evergreen, Colo., the Denver suburb where Hinckley lived and his parents still reside, people voiced similar sentiments last night, though there were signs of empathy for his parents.

"Everyone at my home is really mad. Mom and Dad are really outraged," said Kristen Krause, a student at Metropolitan State College. " . . . I personally don't think the guy was insane. Troubled, but not insane," Krause said.

"Clearly, some screws are missing. He should not be out in the streets," said Neil Rudolph, a real estate investor. Rudolph lives in the same affluent Hiwan subdivision as oilman John Hinckley Sr.

"I think it's a great tragedy. I hope the family can put their life together. I think there was a crime committed but I have a lot of empathy for the parents," said publisher Jon DeStefano, 36.