The president may yet bend on raising taxes and even on Star Wars, but there isn't the slightest expectation that he will abandon his conviction that the exclusionary rule is the bane of law enforcement. The rule -- applied by the Supreme Court to federal officers in 1914 and to the states in 1961 -- forbids the admission in court of evidence illegally obtained by the police.

Addressing a group of law enforcement officers and prosecutors recently, the president proposed legislation that would codify a 1984 Supreme Court decision providing a "good faith" exception to the rule. Under this exception, if a police officer executes a search warrant that he believes, in good faith, was properly issued, the evidence can be used by the prosecutor even if the warrant turns out to be defective. The president, moreover, wants to expand that exception to cover searches made without a warrant, thereby making the core of the Fourth Amendment obsolete.

Critics of the exclusionary rule claim that it does not deter illegal police conduct and thereby only serves to allow criminals to go free on "technicalities." They do not mention former justice Louis Brandeis' point that a court which admits tainted evidence is thereby itself tainted.

As for the deterrence factor, the summer 1987 issue of The University of Chicago Law Review includes a long, precisely detailed study by Myron Orfield that explores the actual effects of the exclusionary rule on officers in the field. By contrast with the views of the president, who has never himself made a collar, a Chicago police officer says in the article, "Of course, there has to be an exclusionary rule. I don't want this to be a police state."

Orfield conducted extensive interviews with 26 Chicago narcotics officers. He focused on that division "because motions to suppress are made in narcotics cases far more frequently and successfully than in any other area of police work."

Through having had evidence suppressed, these officers have acquired a postgraduate knowledge of the law of search and seizure. "As a young cop," said one of them, "I learned that I'd better have a good reason before I search a car. I'd better have more than just 'apparent drunkenness.' "

Said another officer: "Before stopping people in a neighborhood at a late hour, you better have a good reason. Just late hours is never enough. I used to think that saying 'late hours' was enough."

"You get evidence suppressed," said a third, "and you try to do it differently from that point on. And that's all there is to it."

These officers have also learned that when cases are thrown out of court because an officer took short cuts, there can be unpleasant professional consequences. If it happens often, the officer may be transferred or demoted. And he can become a pariah among his peers. Such a pattern of carelessness "would indicate," says a detective, "that the officer is an idiot and an incompetent. No one would want him around." Worse yet, if a cop "violates someone's rights, you could go to jail around here. I know that."

Some officers do still resent the exclusionary rule. But Orfield found that another important dividend of having it in place is that in the company of such aggrieved cops, "several officers said they appreciated the rule because it gave them a reason, within their peer group, to act properly." In the allegedly good old days of unfettered police departments, a cop who questioned the legality of the fruits of his colleagues' searches was not considered likely to advance very far.

The officers interviewed for this study are in favor of a "good faith" exception to the exclusionary rule -- but not nearly so huge an exception as the president's recommendation that searches without warrants be part of that loophole. Having come to understand the value of building cases with care, these cops fear the consequences of dismantling the exclusionary rule by means of vague and overbroad definitions of "good faith."

"By good faith," says one officer, "I mean after the search has been discussed and approved by superiors." Otherwise, says another, "the officer could say anything was good faith, right?" And a third cop: "Pure good faith is too much room to give a policeman."

Altogether, these Chicago police want the exclusionary rule retained because it works. Says Cmdr. John Ryle, head of the Narcotics Section of the Organized Crime Division of the Chicago Police Department: "It is not a detriment to police work. In fact, the opposite is true. It makes the police department more professional . . . in this unit, seldom, if ever, does the law of search and seizure keep us from making the searches we should be able to make."