LAST WEEK, during a visit to San Francisco (no, I wasn't investigating the "sex tents" mentioned in an earlier column), I took the ferry to Alcatraz Island and had an epiphany: We need another Rock.

Before the rehabilitation crowd starts squawking like some of the exotic birds studied by Robert "Birdman of Alcatraz" Stroud, hear me out.

Rehabilitation has been the gold standard of the U.S. penal system for the last half century.

Experts in the field have reached a consensus that imprisonment is simply a bridge between criminal activity and reintegration into society. (We're hearing a lot about that from the administration in City Hall.)

But it wasn't always this way. Alcatraz is a prime example of a different philosophy, one that fell out of favor in the '60s and was ratified by the Warren Court's manipulation of constitutional law.

Before 1934, when Alcatraz officially opened, the charter of the Federal Bureau of Prisons was focused on "restitution and rehabilitation." But a wave of criminality triggered by Prohibition flooded society with a different strain of felon, one just as likely to continue his illegal activities from behind bars and who didn't respond to any "kindler, gentler" treatment in the correctional system.

People like Al Capone, Machine Gun Kelly and Alvin Karpis. They were the catalysts for Alcatraz, the first Supermax facility.

THOSE who were sent to Alcatraz had already acted out at other storied federal facilities, like Leavenworth.

It wasn't so much the severity of the crimes they'd committed (many inmates at the Rock were convicted of nonviolent offenses) but rather their inability to be controlled. The typical Alcatraz inmate was someone who had abused the rules at a prior detention center, engaging in fights with other prisoners or attempting numerous escapes.

And that explains the quotation printed in letters 12 inches high on a sign at the entrance to the prison:

"Those who violate the laws of society go to prison, those who violate the laws of prison go to Alcatraz."

Alcatraz was a major step in emphasizing control over rehabilitation in the federal system, to focus on breaking the criminal spirit and coercing - not cajoling - compliance. And while many disagree with that philosophy and cling to the utopian belief that almost any soul can be saved by kindness, a trip through the corridors of the Rock convinced me that there is a place in this world for the idea of punishment and retribution.

During the almost two- hour tour, we had the opportunity to listen to the recorded testimony of some former prisoners and guards. They all confirmed that Alcatraz, by providing only the minimum comforts required by law (food, shelter, clothing, medical attention), was a prison that acted as a deterrent.

One particularly poignant testimonial came from a man who said he entered as a hardened criminal who didn't care about his family, much less society at large, and left with a determination to live a newly exemplary life. And he did.

Some might say that fear is a poor motivator, and that you can't deter with coercion.

But take a look around at our own troubled streets. Our sister paper has been running a compelling series this week detailing the flaws in our criminal-justice system.

Much of the blame for its dysfunctional performance can be attributed to the fact that it's become a system that shies away from incarceration and tries the kid-glove approach far too often.

The three fatal "P's" - plea bargains, probation and parole - frequently make a mockery of both victims and the prosecutors and police officers charged with protecting them. Add to this judges who too often err on the side of the criminal, and we now find ourselves in crisis mode.

As I wandered down the empty corridors of Alcatraz's notorious D Block, where the worst of the worst were housed in solitary confinement, it occurred to me that retribution shouldn't be a dirty word.

Those who plead for lenient treatment of juvenile rapists, who claim that racial disparities decimate minority communities (actually, the decimation is worst on the victims of the crimes) and who lobby against the death penalty even for the most heinous of murders seem to have lost any sense that certain behavior doesn't respond to kind words and a cup of tea.

Alcatraz was closed in 1963 by a Justice Department led by Bobby Kennedy. The official reason was lack of money.

But many system insiders believed that real reason was that the '60s philosophy of redemption and rehabilitation made Alcatraz an unwelcome anachronism. The pendulum had shifted.

Maybe it's time for another shift. Especially here in a city where the criminals seem to be getting more attention and concern than the victims.

Christine M. Flowers is a lawyer. See her on Channel 6's "Inside Story" Sunday at 11:30 a.m. E-mail cflowers1961@yahoo.com.