by Todd Feurer, CBS Chicago web producer

CHICAGO (CBS) — Mayor Lori Lightfoot is defending her decision to remove former Police Supt. Eddie Johnson from his position as the city’s top cop before an inspector general’s investigation is completed into Johnson’s drinking and driving incident, noting she has the discretion to fire any city commissioner for any reason she sees fit.

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Chicago Fraternal Order of Police President Kevin Graham, in an interview with the Sun-Times, accused the mayor of denying Johnson due process by firing him as superintendent before the investigation was complete.

On Thursday, the mayor denied jumping the gun on firing Johnson, saying Graham is “dead wrong,” and noting she has the authority to fire any city commissioner with or without cause.

“The superintendent, like all commissioners, serves at the will of the mayor. We’ve had repeated conversations, Mr. Johnson and I, about the incidents of that night. I read the inspector general’s reports and reviewed the underlying evidence, and made a determination that I needed to make a change, and that’s precisely what I did. That’s solely within my province,” she said.

The mayor also denied Graham’s claim that she fired Johnson in order to make the case for hiring a department outsider as the next superintendent.

“That’s silly. That’s not what this was about. This was about a specific set of facts and circumstances related to a particular individual, and that’s on the basis that I made my decision,” Lightfoot said.

Former Los Angeles Police Chief Charlie Beck has taken over as the interim superintendent at CPD while the Chicago Police Board conducts a search for three finalists to nominate for the permanent job.

While four high-ranking officers have retired, and one other has been demoted since Johnson’s ouster, Lightfoot said she doesn’t expect Beck to make wholesale changes to the department’s top ranks.

“I expect him to make sure that the Chicago Police Department focuses on its primary mission, which is to keep residents in every neighborhood safe. That’s why he’s here,” she said.

Lightfoot fired Johnson as superintendent on Monday, but he remained on the force, returning to his last career service rank as a lieutenant. He remained on the CPD payroll until Wednesday, when he officially retired.

Although the mayor had the power to remove Johnson from the exempt ranks of the department, because he was a sworn officer, she could not immediately fire him entirely. His attorney, Thomas Needham, said after Johnson’s ouster as superintendent, he wanted to wait to retire until he was assured there would be no gaps in his health insurance. That apparently happened late Wednesday, when he retired.

As CBS 2’s Charlie De Mar reported, sources said other high-ranking officers within the Chicago Police Department could also fall for their silence if they have direct knowledge of the October night when Johnson was found slumped behind the wheel of a sport-utility vehicle.

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Lightfoot declined to speculate if any other officers tried to cover up the circumstances of the incident, citing the ongoing inspector general’s investigation.

“I want to make sure that that investigation remains independent, that the inspector general calls balls and strikes as I know he and his team will do,” she said.

Likewise, the mayor would not say how much information from the inspector general’s investigation would be made public once the probe is complete.

Earlier this year, the City Council approved an ordinance allowing the city to release sensitive inspector general’s reports when they involve findings of conduct that “is, or may be, a felony as defined in the Illinois Criminal Code and is of a compelling public interest.”

Lightfoot said once the probe of the Johnson incident is complete, city attorneys will evaluate whether some or all of the report can be released to the public under that ordinance.

“But we’ve got to be patient, and allow the IG’s work to continue, and I know he’s working diligently to get the investigation completed,” she said.

Johnson was found asleep behind the wheel of his SUV early on Oct. 17, after he said he had gone out for dinner with a group of friends the night before. Speaking before a Police Board meeting the evening after the incident, Johnson blamed the incident on a mix-up in which he failed to take his blood pressure medication, and a feeling that he might faint that prompted him to pull over and rest.

Lightfoot later told the Sun-Times that Johnson had admitted to her in a phone call that he’d had “a couple of drinks with dinner” that night. Johnson announced on Nov. 7 that he would retire at the end of the year, but on Monday, Lightfoot fired him a month early – saying he lied about the October incident.

Lightfoot declined to go into specifics about what Johnson lied about, “out of deference to his wife and children,” but sources told CBS 2 Johnson had been out drinking with a woman who was not his wife hours before he was found asleep at the wheel.

Johnson has denied misleading the mayor or the public, but has apologized for a “lapse of judgment” in the incident.

Sources said the woman with whom Johnson had been drinking that night at Ceres Café, in the Board of Trade Building at 141 W. Jackson Blvd., is also a Chicago Police officer.

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Sources also said 9th (Deering) District officers responded to the 911 call about finding Johnson asleep at the wheel in Bridgeport near his home. Johnson’s wife is a lieutenant in that district.