The attorney for Mark Strong Sr. said Wednesday that he will seek sanctions against prosecutors if they cannot back up their assertion that evidence of child pornography was on a computer hard drive that police seized from Strong’s home. Daniel Lilley made the threat a day after York County Deputy District Attorney Justina McGettigan said in a court proceeding that “markers” of possible child pornography were found on the hard drive taken from Strong’s home in Thomaston during the investigation of an alleged prostitution operation in Kennebunk. If prosecutors cannot prove that, Lilley said, he will try to have them sanctioned…