King County prosecutors have decided not to file criminal charges against Seattle police Officer Ian Birk in the fatal shooting of woodcarver John T. Williams, according to sources familiar with the decision. Prosecutors have been confronted with a steep legal hurdle in deciding whether to charge Birk with murder or manslaughter. State law shields police officers from criminal prosecution when they claim they used deadly force in self-defense, unless it can be shown they acted with malice and a lack of good faith.