It's the video that everyone's talking about: a New York City police officer body slams a bicyclist in Times Square during a "critical mass" bike ride. Watch it closely, particularly at the 24 second marker.

America asks why. But this kind of brutality is continues, even if most police officers are doing a good job. The New York Times notes that the videotaped incident sheds light of false testimony by police officers, as the cop initially gave a statement that bore no relationship to what later surfaced on the citizen videotape.

Around 9:30 on Friday night, a bicyclist pedaling down Seventh Avenue veered to the left, trying to avoid hitting a police officer who was in the middle of the street.

But the officer, Patrick Pogan, took a few quick steps toward the biker, Christopher Long, braced himself and drove his upper body into Mr. Long.

Officer Pogan, an all-star football player in high school, hit Mr. Long as if he were a halfback running along the sidelines, and sent him flying.

As of Tuesday evening, a videotape of the encounter had been viewed about 400,000 times on YouTube. “I can’t explain why it happened,” Police Commissioner Raymond W. Kelly said on Tuesday. “I have no understanding as to why that would happen.”

But this episode was not just a powerful crash between one bicyclist and a police officer. It may turn out to be yet another head-on collision between false stories told by some police officers in criminal court cases and documentary evidence that directly contradicts them. And while in many instances the inaccurate stories have been tolerated by police superiors and prosecutors, Officer Pogan’s account is getting high-level scrutiny.

Later that night, Officer Pogan composed a story of his encounter with Mr. Long. It bore no resemblance to the events seen on the videotape. Based on the sworn complaint, Mr. Long was held for 26 hours on charges of attempted assault and disorderly conduct.

In other words, the bike rider whom the officers slammed to the ground was held for more than a day on bogus criminal charges. Without the videotape, who knows what would have happened to him?