When Richland County Sheriff Leon Lott spoke to press late Tuesday after videos spread online of Deputy Ben Fields flipping a black 15-year-old student in her chair and dragging her across the room, he discussed the internal investigation and commented on whether race was a factor in the incident, excusing Fields from allegations of racism because, as he put it, "this deputy has been dating an African-American female for some time."

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In effect, what Lott is saying is that because the deputy reportedly dates a woman of color, he is exempt from racial bias. If that sounds familiar, that might be because it's essentially a permutation of the age-old excuse that a lot of white people have used to defend themselves against accusations of racism. It's the "but I have a black friend" trope, and it simply doesn't hold water.

Considering the video footage, this violent incident in South Carolina is much more complicated.

In Fields' case, there is a history of excessive force allegations. A 2014 lawsuit alleges that Fields "unfairly and recklessly targets African-American students with allegations of gang membership and criminal gang activity that is set to go to trial," the New York Daily News reported. That case is set to go to trial in January.

What's more, the defense that Lott offered for Fields at the press conference—that his personal relations with a black woman exempt him from speculation about racism—is factually unfounded.

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The last time this defense entered the national conversation was in 2012, and neighborhood watch coordinator George Zimmerman had recently shot and killed 17-year-old Trayvon Martin in Sanford, Florida. The country was deep in debates over allegations of racism; would Zimmerman have done the same to a white teen as he did to Martin? His Black friend, Joe Oliver, suggested he would.

"I do come from an extremely unique perspective, not just being George's friend, but being an African-American, because I understand the outrage," Oliver told the Grio. "But I am in a unique position, in that I know George. And I know that there's no way he would have put himself in a position where he's in hiding, if he didn't believe he had to save his life."

Some interpreted the defense of Zimmerman from one of his black friends as evidence proving that racial bias wasn't a factor in the fatal shooting. But that claim has been challenged, with research showing that race-based prejudice does exist, even in white men who have black acquaintances.

"[A] 2011 study specifically looking at the impact of interracial friendship on white concern about local crime found that when white people have close relationships with black people, their concerns about crime actually increase," TIME reported. "More broadly, when scholars have studied the racial beliefs, feelings and policy views of whites who have contact with blacks as friends, acquaintances or neighbors, they consistently find that the negative racial perceptions of those whites are substantially similar to the perceptions of whites who have no black friends."

"Friendship with black people—and even being a black person—does nothing to change racial bias. Indeed, almost one-third of black people hold similarly negative views."

The same principle applies to Fields. While the deputy's closeness with one black woman might be interpreted as evidence that he does not maintain racial biases, it does not actually prove anything. The Justice Department and the FBI will have to determine that, pending the outcomes of their investigations.