Martin Halloran, president of the San Francisco Police Officers’ Association, sent an angry letter to District Attorney George Gascón refuting his recent public assertion that the union has tried to block such an investigation with “a dizzying array of stonewalling tactics.” Gascón started the squabble on Jan. 28 with a two-page letter to Lee accusing the mayor of failing to support the district attorney’s efforts to look into a wide array of areas concerning police conduct, including use of force, stop-and-search protocols, and internal discipline. Gascón’s effort to investigate the police began in June when he formed a “Blue Ribbon Panel on Transparency, Accountability and Fairness in Law Enforcement,” expecting that it would receive city funding to look into thousands of police reports written by 14 officers accused of trading racist and homophobic text messages. He identified, for example, several lawyer-to-lawyer meetings. [...] he said police had allowed the panel’s lawyers to ride along with some officers, and added that “there have been dozens, if not hundreds, of calls and e-mails back and forth between representatives of the (union) over the last several months.” Hardly a dizzying array of stonewalling tactics,” Halloran concluded, before adding one small footnote that acknowledged “mildly contentious early exchanges with panel representatives.