It is natural to wonder, though, whether Mixon’s case and career might have played out differently if the video had been widely disseminated. The former Baltimore Ravens running back Ray Rice was essentially ostracized from the N.F.L. last year after video emerged of him punching his fiancée and dragging her, unconscious, out of an elevator. After video emerged of quarterback De’Andre Johnson striking a woman at a bar this year, Florida State dismissed him. Like Mixon, Johnson was a promising freshman at a big-time college program.

“Personally, I think that’s a tap on the wrist, to be suspended for the season, considering the severity of the attack,” said Vanessa Morrison, a women’s advocate at the Women’s Resource Center, a nonprofit in Norman, Okla. “That sends a message about how violence against women is viewed, considering the level and dangerousness of the crime he committed.”

Richard Lapchick, a sports management professor at the University of Central Florida who has studied the issue of college athletes committing violent acts, said the inclination on many campuses was to protect athletes who get into trouble.“A video can make it impossible for them to do that,” he said.

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Mixon did not escape punishment, either from prosecutors or his university. But without the video, he was spared the kind of blackballing others have drawn.

Still, local news media outlets clamored for access to the video. Coming out of high school, Mixon was ranked as the No. 8 player in the country by the recruiting website Rivals.com, a player frequently compared to the former Sooners all-American Adrian Peterson. He was a star before he arrived on campus in Norman.

But well-timed legal maneuverings by Mixon, and an Oklahoma state law, prevented the clip from being released. The judge in the criminal case issued an ambiguous order in August 2014 preventing either party from disseminating the video, perhaps to avoid influencing the jury pool, yet seemingly permitting the video to be made available under public-records laws. And while the Norman Police Department most likely had the discretion to allow the video to be copied, according to a city attorney, it declined the news media’s requests, saying the law required it only to allow “inspection” of the tape. (The Police Department referred inquiries to the city attorney.)