The NY Times reported that the city settled with a protester who was kicked in the head back by a high-ranking police officer in 2003. Apparently the city wanted to avoid trial, because activist Cynthia Greenberg had "planned to offer as evidence a videotape of the encounter." If you watch the video, via I-Witness Video, you can definitely see someone's knee hit Greenberg's head.
The police officer who Greenberg says kicked/kneed her is recently retired Assistant Chief Bruce Smolka. Smolka, who is now works in security for Revlon, was a controversial figure who was a commanding officer of the Street Crimes Unit (his officers shot Amadou Diallo in 1999) and is the "architect" of the Critical Mass crackdown.
While the city says its $150,000 settlement with Greenberg is not an admission of guilt, Greenberg's lawyer Jonathan Moore told the Times, "The fact that they are paying this amount can only mean that they believe a jury would be outraged." Moore also said that Smolka, in his deposition, said that he didn't intend to kick Greenberg and perhaps she hit her head against his knee because she was rocking back and forth.