Add the name of Judge Gene Franchini of Albuquerque, N.M., to the list of America's intelligent and conscientious jurists. Or rather former judge Franchini. The other day he resigned from the bench as a trial judge rather than send a first offender to prison.

The criminal, an honorably discharged Vietnam veteran and a jobholder, had been convicted of aggravated assault with a deadly weapon. A jury found him guilty of pulling a gun in a dispute at a traffic light.

Under a mandatory sentencing law, Franchini had no choice but to imprison the man for a year. Out of conscience, he resigned. He explained that putting this particular offender into the hellish New Mexico state prison--the scene of a blood-bath riot in 1980--would be supporting "insanity and injustice."

The same day that Franchini--"not a wild-eyed liberal judge," he said of himself--was giving American justice this bright moment, President Reagan was maintaining the darkness. He was in New Orleans winning cheers from police chiefs for pledging to support mandatory sentencing laws. Such support is part of Reagan's philosophy that was also applauded by the chiefs: "Men are basically good but prone to evil; and society has a right to be protected from them."

The protection argument is at the heart of any discussion of prisons and criminal justice. Packing off people to prisons and jails, which we are doing now at record rates, creates only the illusion of protection. Everyday about 360 people are released from America's penal institutions. That's some 131,000 a year.

I can't recall ever seeing these figures mentioned when public fears are whipped up by politicians making their it's-time-the-law-abiding-are-protectedfrom-criminals speeches. If, as the Bureau of Prisons states, between 95 and 98 percent of our criminals are eventually going to be back among us at some date, the protection factor is low.

The call to build more prisons--the most recent federal task force asked $2 billion for the job--means that instead of 360 people leaving our overcrowded and often inhumane prisons everyday, the number will increase to 500 or 600 a day. What then?

James Q. Wilson, an analyst of crime and punishment who believes that "we need more prison capacity," avoids this question. He wrote in The Post recently that he knows of "no systematic evidence" that people are worse off for prison: "It may well be that there are some offenders who commit more crimes after having gone to prison and some who commit fewer, but we have few studies that examine these fine distinctions."

While Wilson, apparently a patient man, waits for the study industry to ponder the fine distinctions, are we supposed to believe that prisoners leaving violence-filled cages after five or 10 years are ready to go from surviving the laws of the jungle to obeying the laws of society?

Alvin Bronstein of the Prison Project of the American Civil Liberties Union, and one I find a surer guide in penology than Wilson, states: "We know that prisoners get worse. Recidivism escalates with longer sentences. Once you go beyond six-month sentences, recidivism increases, and the nature of the crimes increases in severity." Bronstein adds that high incarceration rates have no relationship to lowering crime rates.

Judges like Franchini and civil libertarians like Bronstein enrage those who think that criminals get too much help while the victims are ignored. But it is the victims that enlightened judges and penologists are caring about. By imposing other forms of punishment on certain criminals--restitution, fines, community service--they are arguing that there will be fewer victims tomorrow because criminals today were punished humanely.

Judges know that only a small percentage of lawbreakers need to be isolated from society. Judge Franchini was saying only that. He was a hard-line jurist: hard on the prevailing myths and slogans about punishment, and, in the end, hard on the public for making us reflect about his act of conscience.