A federal judge has found that although there was probable cause to believe General Motors Co. committed a crime in failing to disclose a deadly ignition-switch defect, plaintiffs lawyers failed to prove that GM’s outside lawyers at King & Spalding should have to turn over their internal notes and memos on the matter.

Wednesday’s ruling is a setback for plaintiffs lawyers who are suing GM over the defect, which led to 2.6 million cars and trucks being recalled worldwide last year and has been linked to 124 deaths. The first bellwether trial against GM is set for Jan. 11 in New York.