In 1969, AFTER the assassinations, riots and other disorders of that troubled decade, the National Commission on the Causes and Prevention of Violence sketched a portrait of the "typical" presidential assassin. Those who have attacked presidents have been,

"white, male and slightly built."

"Nearly all were loners and had difficulty making friends of either sex and especially in forming lasting normal relationships with women."

"Normal family relationships were absent or disrupted."

"All of the assassins were unable to work steadily during a period of one to three years before the assassination."

"All of the assassins tended to link themselves to a cause or a movement . . ."

"All but [Lee Harvey] Oswald used a handgun."

"At great risk to themselves, nearly all chose the occasion of an appearance of the president amid crowds for the assassination attempt."

On this record, the commission predicted that "the next assassin to strike at a president would have most" of these attributes.

The resemblances between the commission's 1969 profile and John Hinckley are striking. He appears to be just the sort of person we would have expected to do this deed.

Yet Secret Service Director H. Stuart Knight said last year: "There is no profile of an assassin. We keep searching for it, but there is no sure-fire profile." And, of course, he is quite right -- because the profile of the assassin is also the profile of thousands of unhappy individuals who never commit an act of violence. As the Commission on Violence recognized, the personal attributes of its typical assassin, until the moment he strikes, can be found in "many valuable, trustworthy citizens."

But if the profile is not "sure-fire," it is not entirely useless, either. It contains clues to the better protection of the president that are worth pursuing.

The profile identifies the presidential appearance in a crowd as the moment of choice, and it also identifies the handgun as the weapon of choice. The choice of the handgun is not entirely rational: The serious political assassin in more unstable parts of the world would choose a rifle or explosives, and he would have confederates to assist him. Our sick, pathetic American assassin is a loner who chooses a less reliable weapon -- even a "Saturday Night Special" with little "stopping power." To be sure, the concealable nature of the weapon enables him to get closer to the target in a crowd -- but so close that he can have no reasonable hope of escape.

Can we reduce the risk that the potential assassin, the handgun and the president will converge into tragedy? Are presidential discretion and protection a potential discretion and protection a potential variable in this morbid equation, or must we accept the mothlike passion of all presidents to fly close to the flame? Is the handgun a potential variable, or must we take it as a given, a constant, in a nation possessing 60 million such weapons?

There are two major variables in the assassination equation. One is the possibility of stricter limits and controls on the president's appearances amid crowds in public places. A president's chances of being attacked vary in direct proportion to his interactions with uncontrolled crowds of people in unsecure areas.

Is it prudent to announce in advance the president's whereabouts at a specific time, to predict his exact location by the clustering of TV and press cameras, and then to allow unauthorized and unidentified people to approach within a dozen feet of that spot? Was it necessary to have a "photo opportunity" outside the Washington Hilton? Given the available photo opportunities inside the hall where the president spoke -- and where metal detectors could have been used -- was there any purpose for the outside photo opportunity, except to witness -- and inadvertently to cause -- any tragedy that might occur?

And if the outside photo opportunity was a reasonable risk, shouldn't a security perimeter have been established further from the president's path and more carefully controlled by checking press badges? Magnificently as the Secret Service performed from the moment of attack, could there have been a laxness in observing these textbook precautions -- understandable after the lull of several years since the last such attack?

As with the attack on President Reagan, the two unsuccessful attacks on President Ford and the killing of President Kennedy, all occurred when the president was exposed on a street to unscreened crowds of individuals. In a country with 60 million handguns, freely available to the thousands of Americans who fit within the "profile of the assassin," a prudent president must recognize that the streets of this nation are even less safe for him than they are for the ordinary citizen. The Commission on Violence observed that the president can "limit his public appearances to meeting places to which access is carefully controlled, especially by the use of electronic arms-detection equipment." As the commission said: "Effective security can exist if the president permits ."

The second important variable is the handgun. The handgun is not merely the assassin's weapon of choice. It is the choice of the perpetrators of most violent crimes. It has no redeeming social virtue. The Commission on Violence recommended that handguns be both registered and licensed, and that licenses be restricted to those who could show both responsible character and a legitimate need.

The Gun Control Act of 1968, while it bans the importation of many small, cheap handguns, nonetheless permits the importation of Saturday Night Special parts for assembly in the United States, as was true of the handgun used to shoot President Reagan. Chairman Strom Thurmond of the Senate Judiciary Committee is reported to be willing to close this loophole. Sen. Thurmond is also said to be interested in establishing a system for requiring local police to notify the FBI and the Secret Service whenever an individual is arrested with a weapon in the same city near the same time as the visit of a president or a presidential candidate. The FBI was apparently notified of John Hinckley's arrest with three handguns in Nashville, but evidently failed to notify the Secret Service.

Prof. James Q. Wilson and his Harvard colleague, Mark Moore, have suggested more generally that persons arrested "in public place with a gun and without a permit" should be treated far less leniently than they now are. They suggest use of airport-type hand-held magnet meters on street frisks of suspects -- an idea that would seem to especially applicable to persons allowed to crowd into nearby areas as presidents make entrances and exits from public buildings.

The Kennedy-Rodino Handgun Crime Control Bill of 1979, soon to be reintroduced in the present Congress, would prohibit pawnbrokers from dealing in handguns at all, because of the long history of abuse and irresponsibility of these sources of the weapons used in violent crimes. That legislation, based in part on work undertaken by both the Ford and Carter Justice Departments, contains a number of other, more significant provisions sensibly and practicably designed to curb our national irresponsibility about handguns.

There are even stronger measures of great promise we may now be willing to take. One is the proposal that handguns be both registered and licensed. A complementary measure would be grant amnesty and pay a generous bounty for all unlicensed handguns that are voluntarily surrendered within a year after the licensing law takes effect. If they all came in, the one-time cost would be in the range of $1 billion -- a mere fraction of what we now spend annually to deter, detect and punish the crimes these handguns are used to commit.

At long last, we should also act on the 1969 commission's proposal for a major funding commitment to develop better methods of detecting the presence of concealed handguns and ammunition in public places. It should be possible to apply a chemical treatment to all handgun ammunition that would give it a detectable scent which could be picked up by a sensitive "sniffing" device. After President Kennedy's assassination, some of our best scientists suggested that ammunition could also be "tagged" with a low-level radioactive substance readily detectable by a hand-held Geiger counter. Very little has been done to prove out this promising idea.

This president and the members of his party in Congress, if they are prepared to move, can win the passage of many such legislative proposals. They have shown the courage to buck the conventional wisdom as to the political impossibility of sharply cutting government expenditures, and they are turning public opinion around on this issue. The same political courage is needed to control the handgun.

President Reagan has fortunately survived the most recent of these recurring assassination attempts. History has handed him a unique opportunity -- the best any president will ever have -- to reduce the blight of the destructive and despicable handgun on the American social and political scene.

That would surely be better than waiting passively and with bated breath for the next attempt to be made by another loner with access to a handgun and a compulsion to reenact the television drama all of us have just witnessed, just as John Hinckley may have been reenacting the plot of "Taxi Driver."

Immediately after surgery, President Reagan repeated Winston Churchill's just that there is nothing more exhilerating than to be shot at without result. It would be wonderful if this time we could achieve a result -- a happy instead of a tragic one.