San Francisco Fire Department Battalion Chief Kevin Taylor is a commanding figure at more than 6 feet tall, with a firefighter's all-muscle build. But he speaks in soft, measured words, even when making explosive allegations against his employer.

Taylor claims that last summer, a senior SFFD officer helped white colleagues cheat on an advancement exam. By the fall, when the exams had been completed, the city's two black assistant fire chiefs scored somewhat poorly and retired rather than face demotion. Lower-ranking firefighters, meanwhile, placed at the top of a list of officers eligible to be promoted. "And they're all white males," Taylor says.

For Taylor, this was an unfair purge. The accusation is ironic, given that Fire Chief Joanne Hayes-White was recruited in the wake of a 1987 court decree demanding an end to sexism and racism in the department (she declined to comment for this column). And there's evidence she supports diversity: In July, she appointed African-American firefighter Monica Fields as deputy chief.

But the city will now take Taylor's allegations seriously. In a special meeting, civil service commissioners will soon review documents from a Department of Human Resources investigation into the cheating allegations that concluded Taylor's claims were unfounded.

Despite these efforts, I think the inquiry could be more effective — either in exonerating accused cheaters, or confirming Taylor's claims — if it weren't hampered by a conflict of interest where the person in charge of creating and administering the test was also assigned to determine whether cheating nullified its results.

Promotions resulting from this test may involve pay hikes worth millions of dollars over the years, and cheating allegations warrant an independent inquiry.

Complaints of discrimination are so commonplace in local government that managers typically brace themselves for allegations, lawsuits, and appeals any time they make a significant staffing decision. But legitimate claims can emerge through this background noise. And the city's racist history has been partially overcome, thanks to verified discrimination claims.

In 1984, the San Francisco Black Firefighters Association filed a lawsuit describing the fire department as a white men's club. In 1987, a judge approved an integration plan. Court supervision was lifted only after then-Mayor Willie Brown appointed as chief one of the plaintiffs in the 1984 suit.

Slow as they may have been, these court-ordered improvements inspired Taylor. Twenty-three years ago, after spending a decade as a deputy sheriff, he applied to the fire department and found a calling.

" I went to a fire in Hunters Point in 1997 where six people lost their lives," he recalls. "Five of the six were children, up in the housing projects. A couch caught fire, trapping victims upstairs. One of them was burnt to ashes; cremated, more or less. It's something I think about fairly often."

Bolstered with a master's in public sector leadership from St. Mary's College in Moraga, Taylor moved up through the ranks, reaching the position of battalion chief, where he's been for 13 years. Ordinarily, officers advance from battalion chief to assistant chief by taking civil service exams. But until last summer, no such tests had been administered for the assistant chief level since the 1987 court decree. Instead, appointments to assistant chief — one of half a dozen officers citywide in charge when attending major fires — were handled on what was called a provisional basis, even though such appointments often lasted years. Taylor said he was among several officers who served such temporary stints.

By 2010, the last "permanent" assistant chief left from the 1980s was an officer named Art Kenney. Thanks to civil service rules, his title made him the only person qualified to advise the city on how to create a specialized advancement exam for assistant chiefs.

In mid-June, Taylor says he overheard Kenney ask a superior officer, Deputy Chief Patrick Gardener, how one would place a fire truck near a fire. "I said, 'He's tutoring people,'" Taylor recalls. "I said it with such force that Gardener turned and said, 'I don't want to discuss the exam anymore."

By Taylor's reckoning, Kenney was asking Gardener for information to unfairly pass along to lower-ranking white officers. The Department of Human Resources ultimately determined that Kenney and Gardener were merely discussing firefighting tactics, not exam cheating. That interpretation infuriates Taylor. "I'm trained on how to conduct investigations," he says. "I know what I witnessed."

Chris Stevenson, who recently retired as a provisional assistant chief, told me he once overheard Gardener acknowledge that Kenney had inappropriately discussed the exam, but Kenney insists the allegation is bogus. "It's definitely a false accusation. There's absolutely nothing to it," he says. "He [Taylor] must be saying it so often that he's starting to believe it himself. We've been friends for a number of years, and I don't know why any of this has happened. I hope they can reinvestigate it, and that I will again be cleared."

In August, a week before the test was to be administered, Taylor complained to city human resources director Micki Callahan about Kenney's supposed comments. In November, Taylor met with John Kraus, who oversees city employment testing. On Jan. 28, Kraus wrote to the Civil Service Commission and said none of the allegations could be substantiated.

Taylor has appealed this conclusion and demanded a new investigation. This week, a detailed chronicle of Kraus's fact-finding will be delivered to commission members, who must judge which version of events is true.

There's no reason to believe Kraus didn't do his best to assess Taylor's claims. But he's a test-making bureaucrat whose job success is measured in reliable exam results — not cheating-linked debacles.

Many of us may have cheated on a test at one point or another. But not with these stakes. High-ranking San Francisco firefighters are paid extraordinarily well. And the higher the rank, the greater the take. Taylor's base pay last year was $161,895, which became $202,397 with overtime and other pay. Kenney, the city's only official permanent assistant chief, earned $187,146 in base pay plus overtime and other pay for a total of $267,777.

It's during retirement when these differences really pay off. City firefighters earn 90 percent of their annual pay upon retirement, which for many officers begins in their mid-50s. In two or more decades, a single officer's exam-facilitated pay bump can be worth half a million dollars. The test in question may affect half a dozen such positions.

Cheating allegations involving multimillion-dollar payoffs fall under the category of potential white-collar fraud, and warrant an outside investigator with enough resources, authority, and leeway to find the truth.