STOCKTON, Calif. — A woman kidnapped, raped and murdered an 8-year-old girl whose body was found in a suitcase dumped in a pond just a few miles from home, prosecutors alleged Tuesday. Melissa Huckaby, 28, was charged with murdering her daughter's playmate, Sandra Cantu, in a gruesome crime that has shocked and terrified residents of Tracy, a Northern California city of about 78,000, 60 miles east of San Francisco. Huckaby, who volunteered as a Sunday school teacher at her grandfather's Clover Road Baptist Church in Tracy, appeared in a San Joaquin County courtroom for her arraignment in a red jumpsuit and shackles.