Spokane County prosecutors are following colleagues from King, Pierce and Clark counties in saying they will no longer prosecute adults 21 and older for possession of less than an ounce of marijuana. “We are not going to prosecute any new cases,” said Jack Driscoll, chief criminal deputy Spokane County prosecutor, following passage last week by Washington voters of a marijuana-legalization law. “After Dec. 6, it is legal to possess an ounce” if you are 21 or older, he said.