CEDAR RAPIDS — A judge Thursday denied a prosecution’s motion to have joint trials for two 17-year-olds accused of killing Malik Sheets last summer and two others accused of helping cover it up. Marshawn Jeffries and Christian Emedi, both 17, of Cedar Rapids, will be tried together, but First Assistant Linn County Attorney Nick Maybanks also wanted the trial to include Jeffries brother, Miguel Ruiz, 24, and Aleah Anderman, 17.