A woman convicted of killing her parents when she was a teenager and sentenced to two life terms in prison has been denied a new trial.    Fifth District Court Judge G. Richard Bevan on Monday ruled that 24-year-old Sarah Johnson did not have ineffective legal counsel at her 2005 trial.      The Idaho Mountain Express reports that Bevan also ruled that new fingerprint evidence brought forward after her conviction wasn't sufficient to order a new trial.      Authorities say that in 2003, the then 16-year-old Johnson shot and killed her mother and father at their Bellevue home following a dispute she had with them over her boyfriend.      Johnson's attorney, Christopher Simms, says he will appeal.