Despite overwhelming public support for him, the great majority of politicians and commentators, including James Fyfe ("Vigilante, Holster Your Gun," Outlook, Jan. 6), have condemned the action of a New York City man who shot four men attempting to extort money from him. They argue that it was improper, probably illegal, and not the right answer to the problem of rampant crime. Yet each year thousands of law-abiding citizens gun down criminals who threaten them, and their acts are not only entirely legal but may also be a very effective means of deterring crime.

Under one of the oldest legal principles known to mankind -- one common to all legal systems and said to derive from the same "natural law" that justified the American Revolution -- any citizen has a legal privilege to use deadly force whenever he reasonably believes he is being threatened by serious bodily injury. In many cases, the same privilege applies to defending others or to preventing the commission of a serious crime.

It is not unlikely that a jury composed of ordinary New York City citizens who are forced to ride the subways will find that Hugo Goetz had such a reasonable belief when the four surrounded him and demanded five dollars. He knew, apparently from personal experience as well as common sense, that thugs who make such requests frequently have and use deadly weapons. In this case, they were carrying sharpened screwdrivers and had long criminal records.

Indeed, if only one juror out of 12 finds Goetz's belief reasonable, or determines in conscience that justice will not be served by punishing him, Goetz cannot be convicted; and a verdict of "not guilty" for whatever reason cannot be appealed and otherwise attacked, no matter how wrong or contrary to the law prosecutors believe it to be. One of the reasons the Constitution protects the right to a jury trial is to permit the common man to nullify the law when it operates in ways contrary to his own common-sense notions of justice.

Although it is claimed that Goetz told police that he intended to kill the punks who threatened him, jurors may still find that his belief that the shooting was necessary a reasonable one and thus his action perfectly legal. A frightened citizen facing four assailants bold enough to accost him in public is not required to act with the skill and cold determination of a trained police officer who knows that backup is on the way, and even a trained officer trying to frighten or arrest four different assailants in a moving train is likely to get himself or an innocent passenger injured. In any event, others who may follow Goetz's example would be well advised not to make any statements whatever until a lawyer has advised them of the legal consequences of certain admissions.

While many have argued that self-defense is not the answer to rampant crime, it may be an answer that is as effective as any other. Studies show that in California citizens legally kill twice as many felons each year as law enforcement officials do, and the ratio rises to three-to-one in cities such as Chicago and Cleveland. And considering the ineffectiveness of the criminal justice system with its many loopholes and ineffectual sentences, it is not surprising that the threat of being shot is often a far more effective crime deterrent than the threat of being caught.

For example, rape dropped 90 percent in Orlando, Fla., after a highly publicized program in which women received defensive handgun training. Although rape in the surrounding area increased over 300 percent during the next five years, it remained below the initial level in Orlando, where would-be rapists faced an unappealable death sentence from a potentially armed victim. Similarly, grocery robberies dropped 90 percent following a widely publicized firearms training program for Detroit grocers and the shooting of seven would-be robbers. In the District of Columbia homicide dropped 36 percent in the five years prior to a handgun ban, and then rose 16 percent in the five subsequent years, while it decreased 9 percent in neighboring Virginia, which has no such laws.

Until municipalities both recognize and fulfill a duty to make our streets, subways and other public places reasonably safe, we must expect that at least some people will find themselves forced to defend themselves in situations that reasonably seem to require it. Far from acting as "vigilantes" or "taking the law into their own hands," they are simply exercising a legal privilege citizens have enjoyed since long before the creation of modern police departments. While it may not be in the best long- range answer to the crime problem, it is an answer that may be as effective as our current criminal justice system, and one that will continue until other proposed "solutions" provide reasonable protection to a justifiably frightened and frustrated public.