A judge has scheduled a preliminary hearing to start Nov.18 for a mother accused of being an accessory and dissuading a witness in connection with the shooting of two teenagers outside a north Modesto apartment complex last year. Authorities say Nanci Sue Blackwell tried to prevent a witness from giving investigators information regarding a crime, according to a criminal complaint filed April 23 in Stanislaus County Superior Court. She also is accused of harboring, concealing or aiding a felony suspect to avoid capture, as well as possession of methamphetamine. She has pleaded not guilty to the charges. At the conclusion of the preliminary hearing, the judge will determine whether there is enough evidence for the case to proceed to trial. Her sons, Robbie Blackwell and Nicholas Spangler, are accused of murder in the deaths of Rolando Luna and Andrew Ensey. The shooting occurred about 9:15p.m. Feb. 10, 2012, in the 2400 block of Vera Cruz Drive near Floyd Avenue. In late March, Melanie Martin said in court that she withheld information on the witness stand because she was threatened by the defendants mother. Martin testified that Nanci Blackwell told her not to tell authorities everything or shed f--- me up. The judge has scheduled a trial to start May 6 for Robbie Blackwell and Spangler. The mother and her sons remain in custody at the Stanislaus County Jail.