A Koran sits open on the highest shelf in the Philadelphia police commissioner's office. A nameplate on his desk, an Egyptian souvenir from his son the FBI agent, spells out "Sylvester Johnson" in curlicued Arabic script.

The office props point out a background that Philadelphia's top police official is otherwise low-key about: He is a Muslim.

He might be the only police chief in the country who is; five national Islamic advocacy groups who track the accomplishments of Muslims know of no other.

Johnson's faith -- a rare one for a public official in the United States -- became an issue for some in the city last month when he publicly contradicted and upbraided his department's counterterrorism chief, Inspector Joseph E. O'Connor, who had angered local Muslims by saying the city was "notorious" for funding and recruiting terrorists.

Johnson, in a rare interview focusing on his faith, acknowledged that Islam did shape how he handled the fallout from O'Connor's comments Sept. 1 at the Al-Aqsa mosque. Despite murmurs from some quarters that he goes to mosque only for political show, he said his race and his religion have affected his approach to his job, sensitizing him to unfair branding of any group.

"That's wrong, to say that mosques in Philadelphia harbor extremist people . . . unless you come out and be more specific," Johnson said.

"Islam does not teach killing people. Islam does not teach crime. Islam does not teach violence or terrorism. That is not Islam," he said. "For him to make that statement, and blanket the entire Islamic community, is totally wrong."

Johnson became a Muslim after joining the police force in the mid-1960s, when the Nation of Islam gained adherents in neighborhoods across the country with its message of self-reliance and black power. He said the racist slurs to which he was subjected as a young officer on the beat -- and the roughhouse demeanor of his fellow police officers toward his fellow African Americans -- drove him to a Nation temple. The sermons against racism and police brutality resonated.

Although Islam gave Johnson the strength and discipline to cope, it also complicated his life on the force. The head of homicide -- the department in which Johnson worked -- questioned him about his belonging to the Nation of Islam. Johnson did not deny it and none of his colleagues wanted to work with him.

"It was uncomfortable because, really, people in the Nation didn't trust you because you were a police officer," he said, "and people in the police department didn't trust you because you were a Muslim."

The department has come a long way -- as has Johnson -- since he converted and became one of its first Muslim officers. Muslims number in the hundreds on a force of 7,000.

Johnson no longer belongs to the Nation of Islam. He worships at a mosque tied to Warith D. Muhammad, the Nation leader who broke with the group because of its separatist philosophy and urged his followers to become mainstream Sunni Muslims.

Most of Johnson's family -- his wife and two of his three sons -- are not Muslim. Some question how "Muslim" the police chief is himself.

"He's someone who says he's a Muslim. There's a difference between a Muslim and a practicing Muslim," said police Officer Kenneth Wallace, a Muslim.

Wallace grew his beard beyond the Philadelphia department's quarter-inch regulation length in observance of Islam and was ordered home until he trimmed it. Following the example of the prophet Muhammad, many Muslim men wear beards, and some scholars say it is a religious obligation.

Wallace is in a standoff with the department, waiting to be told whether he is fired. Johnson is not backing him, just as he did not support a female officer who wants to wear the hijab, the traditional Islamic head scarf, with her uniform.

"You don't wear religion on your face," the commissioner said. "You wear it in your heart and mind."

The stance has not won him friends among some Muslim leaders.

"He seems determined to show he's not going to favor Muslims," said Isa Abdul Mateen, imam at the Masjid al-Quran mosque in Philadelphia. "That was good of the commissioner to say what he did [about O'Connor's statement]. It's good that he's not totally turning his back on the Muslim community, just partially."

Still, Johnson, citing religious freedom and civil liberties, had department rules rewritten to allow officers to wear a beard -- within limits. He wants an imam who instructed U.S. soldiers heading to Iraq on Islamic customs to do the same for his officers and for trainees at the police academy.

And he considers it a duty to maintain friendly ties with mosques in Philadelphia -- and to defend them against charges of coddling terrorists. "What history shows us is, a lot of terrorists have used the religion of Islam," he said. "If you have a good relationship [with the Muslim community], these are the people who will bring them to our attention."

Marwan Kreidie, head of the Philadelphia Arab American Development Corp. and an organizer of the Sept. 1 sit-down at the Al-Aqsa mosque with O'Connor, said Philadelphia police are fair when it comes to Muslims in a post-Sept. 11 world.

"The police department is such that people in the Arab American and Muslim community feel safe in Philly [while] people get stopped in the suburbs based on ethnic looks," Kreidie said. "And that's a view that comes from the top."

"Islam does not teach crime," says Philadelphia police commissioner Sylvester Johnson, in his office.