Thoughout his article, "Don't Loosen Curbs on Illegal Cop Searches," (Outlook, Feb. 27) James J. Fyfe refers to "police misconduct" or "illegal searches" conducted by the police. But this is not the issue being considered by the Supreme Court. Illegal searches and police misconduct are reprehensible and should be prevented from occurring. What is at issue before the Supreme Court in the case of Illinois v. Gates is the question of whether the police officers were acting in reasonably good faith when they searched the home and automobile of Lance and Susan Gates, pursuant to a search warrant that was obtained from a neutral magistrate and therefore was presumably valid.

The police in Bloomingdale, Ill., received an anonymous letter stating that the Gateses made their living selling drugs and that they soon would be traveling to Florida and returning with over $100,000 in drugs in the trunk of their car. The police corroborated such facts as the address of the Gates, their automobile license number, that Mrs. Gates had driven to Florida and checked into a motel room, that Mr. Gates flew to Florida and visited a woman registered in the motel as Mrs. Gates, and that the couple left Florida together.With this information, the police applied for and were issued a search warrant, which they executed upon the Gateses' return.

It is the contention of the International Association of Chiefs of Police that the police officers followed professional procedures and took all reasonable steps available to them to corroborate the information contained in the letter.

Fyfe contends that individuals and groups that filed amicus curiae briefs on behalf of the State of Illinois are requesting the Supreme Court to sanction well-meaning but illegal police searches and seizures. That is not the case. What my organization has argued is that the evidence obtained pursuant to a search warrant should not be excluded if the officer was acting with a reasonable good-faith belief that his actions were legal.

This exception to the exclusionary rule, if it were adopted, would be strictly limited. The police officer's actions would be subject to an objective test and would have to be based on premises that can be articulated and that are sufficient to cause a reasonable, and reasonably trained, officer to believe he is acting lawfully.

The exclusionary rule is judicially created, not mandated by the Fourth Amendment, which guarantees that persons, houses, papers and effects shall be secure against unreasonable searches and seizures. When the rule was first imposed on federal courts, the justifications offered were those of deterrence of illegal police conduct and maintenance of judicial integrity. The deterrence ground was based on the theory that if the police could not use illegally obtained evidence for prosecution, they would have no incentive to gather evidence by improper means. Judicial integrity would be maintained by preventing courts from being "accomplices in the willful disobedience of a Constitution they are sworn to uphold."

Over the years, the deterrence rationale has become the court's primary emphasis; the judicial integrity argument has been all but abandoned. Yet no effort has been made to distinguish between the types of police misconduct asserted in different situations.

Suppose a police officer acts in a good-faith belief that his actions conform to the letter of the law, only to find out later that the date was missing on a search warrant affidavit or a statute is found to be unconstitutional. He faces the same exclusion of evidence as the officer who intentionally and substantially violates an individual's constitutional rights.

To be sure, at the time the rule was created, it seemed that the goal of deterring police misconduct could be reached by suppressing unlawfully obtained evidence. But the deterrence rationale is substantially weakened where good-faith violations constitute the "misconduct." If an officer is not aware of his violation, he certainly will not be deterred by the suppression of the evidence he secured. Indeed, there is no misconduct to be deterred.

Moreover, although the exclusionary rule is aimed at police, no sanctions are directed toward them if they secure evidence improperly. The application of the rule punishes society in the long run, for a criminal, often a dangerous one, is released to continue his unlawful behavior.

It is also worth noting how unrealistic it is to expect the police to apply unerringly the complex, frequently changing laws of search and seizure. Often they are confronted with life-threatening situations where decisions must be instantaneous, and the legal ramifications are superseded by the requirements of the moment.

The search for truth is diverted when relevant and reliable evidence is kept from trials. The guilt or innocence of the accused is the focus of a criminal trial. This determination should be aided with the use of probative evidence, often directly supplied by the suspect himself. A rule that mandates suppression of trustworthy evidence undermines the confidence of the public in our criminal justice system.

Finally, Fyfe indicates in his article that the exclusionary rule affects few cases. He cites a recent study conducted by the National Institute of Justice, which examined 874 burglary, robbery and assault cases in San Diego and Jacksonville, Fla., and concluded that only nine burglary cases were dismissed because of illegal searches and seizures, and not a single robbery or assault case was affected at all. Not mentioned is that this same study concludes that 4,130 cases--4.8 percent of all felony arrests rejecteddfor prosecution in the State of California between 1976 and 1979--were not prosecuted because of search and seizure problems.

Application of the exclusionary rule in cases such as Illinois v. Gates, where the police have acted in objective and reasonable good faith serves no good purpose whatver but rather harms us all.