The confrontation between police and protesters near the 16th Street Mall during the first day of the Democratic National Convention in August was not instigated by the actions of an undercover officer. That's the conclusion of Denver's independent police monitor, Richard A. Rosenthal, in a letter to an attorney for the American Civil Liberties Union of Colorado, according to The Denver Post . The ACLU had alleged that an undercover officer staged a confrontation with police Cmdr. Kris Kroncke in order to escape the crowd, in turn inciting the mass. But Rosenthal wrote that the officer's action was "reasonable" and says that he will take no action, adding that police believe an "immediate risk to public safety" justified their actions. The ACLU has also filed a series of complaints regarding the mass arrest on August 25 on 15th Street near Civic Center, claiming police lied, in sworn statements, about giving a dispersal order and the crowd ignoring it, according to the Rocky Mountain News . The ACLU says police have withheld 15 minutes of audio dispatch tapes that would clear those facing trial of wrongdoing.