The head of Philadelphia's police union has called Philadelphia District Attorney Seth Williams "a morally and ethically challenged sideline playboy" after the DA's Office declined to pursue criminal charges against a 16-year-old girl who fought with a police officer in West Philadelphia.

In a blistering statement issued Wednesday afternoon, John J. McNesby, president of Fraternal Order of Police Lodge 5 and a frequent critic of Williams, said the DA "has chosen to disregard his responsibility and look the other way when a Police Officer is assaulted."

"The young woman who freely admitted assaulting a uniformed Officer on duty is allowed to walk away with absolutely no accountability by a District Attorney too busy dodging Federal Subpoenas to do the job he was sworn to do," McNesby said. A federal investigation has resulted in subpoenas to Williams' campaign and to a nonprofit he started.

Williams' office responded with a statement criticizing McNesby's comments.

"District Attorney Williams will never apologize for relying on high investigative and prosecutorial standards before deciding to take away someone's freedom," said the statement from office spokesman Cameron Kline. "And it's stunning that anyone, much less a member of law enforcement, would ever believe anything else."

Police on Tuesday said the 16-year-old girl - whom they have not identified - admitted to slapping a female officer in the face during a wild brawl around 2:45 p.m. Monday on the 1300 block of South 54th Street.

A video posted on social media did not capture the alleged slap, but showed the officer - also not identified by police - responding by throwing the girl on the ground and swinging fists at her face.

Commissioner Richard Ross said the 12th District officer had been removed from street duty pending an Internal Affairs investigation.

Police had recommended that the girl be charged with assault of a police officer and related counts, but Williams' office decided to drop the case, citing "a review of the evidence." A spokesman Tuesday declined to elaborate.

McNesby said the situation echoed Williams' decision in April not to file charges against LeSean McCoy, a former Eagles running back accused of assaulting off-duty police officers inside an Old City nightclub. McNesby on Wednesday called that case a "debacle in which Williams turned against the police."

"Philadelphia's citizens and Philadelphia Police definitely deserve better," McNesby concluded.

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