POLICE Commissioner Sylvester Johnson has aggressively denounced the stop-and-frisk policy proposed by incoming Mayor Michael Nutter.

The law-enforcement strategy to get illegal guns off the street would be "a disaster," Johnson has said, claiming it would shatter the unprecedented peace he's forged between police and the community.

"While I'm the police commissioner, I'm not going to do it," Johnson was quoted in Friday's New York Times, in the latest salvo.

Only one problem: the department already is doing it, according to another police official who testified at a City Council hearing.

And if you press Johnson for an explanation, as I recently did, he acknowledges as much - and changes his tune.

"I am not against stop-and-frisk," he told me. "I think it's a good tool.

"We've been doing it ever since I've been in the Police Department, the last forty years."

He even boasted that last year, Philadelphia confiscated more guns - 6,000, according to him, or 4,500, according to the department's press office - than any other city in the country.

What he opposes, he said, is "illegal stop-and-frisk."

"If you don't have probable cause or reasonable suspicion, then you should not stop, it is unconstitutional."

Unbelievable.

In his adamant public comments, Johnson never bothered to stipulate that he was talking about illegal police activity.

But who in his right mind - not to mention someone as smart as Michael Nutter - would publicly propose an illegal policy?

"We will legally, constitutionally pursue illegal weapons in the street," Nutter said in oft-repeated sentiments the day after his election.

"One thing we will not do is abuse the rights of citizens," incoming Police Commissioner Charles Ramsey emphasized the day Nutter announced his appointment.

The truth is, stop-and-frisk has been upheld as constitutional, so long as there's probable cause and reasonable suspicion to stop someone.

Is a pocket on one side weighted down? Is there a bulge in a civilian's midsection? Does he adjust something unseen when he changes position? Is his head uncovered in rain or snow although he's wearing a hooded coat (suggesting a gun might be in the hood)? Is his coat unbuttoned in the cold, enabling quick access to a weapon?

An FBI report says police trained to make such observations "and the combined context in which they occur" can justify citizen stops.

The tactic, when appropriately applied, has withstood legal challenges and made a difference in some communities, experts have said.

No one is suggesting a replay of Operation Cold Turkey - which Johnson cited as the example to me - when Latino residents of Fairmount were detained indiscriminately in the aftermath of the 1985 murder of Police Officer Thomas Trench.

So who cares what Sylvester Johnson says?

After all, he's a month away from retirement. And his reputation has been damaged by the city's gun violence.

But it's not OK for the police commissioner to attack the city's incoming mayor on an issue they fundamentally agree on. It's a cheap shot - and could potentially hamper Nutter's ability to win public support for the policy.

While opinion-makers have trashed Johnson for his defensiveness and failures of leadership, many regular citizens genuinely respect him.

The detente he's created with the public after years of tension and distrust was most apparent to me during the search for Officer Chuck Cassidy's killer.

Although video showed police speeding down streets and kicking in doors, there was little public backlash - except for families who lamented police failure to pursue the killers of their loved ones with equal fervor.

It's urgent that Nutter be well received by these same residents.

And wrong of Johnson to try to damage that possibility by discrediting one of Nutter's key proposals.

Especially when he's already using it. *

E-mail porterj@phillynews.com or call 215-854-5850. For recent columns:

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