ST. JOHNSBURY, Vt. (AP) — A man told police he poured vodka into the IV feeding tube of his girlfriend’s disabled 13-year-old son to settle him down, a dose of alcohol that contributed to his death, according to court documents released Wednesday.Walter Richters and Melissa Robitille, both 38, were charged with second-degree murder in the Aug. 22 death of Isaac Robitille. They entered not-guilty pleas at their arraignment Wednesday afternoon in Caledonia County and were ordered held without bail. Neither spoke.“There is great evidence of guilt,” said Maria Byford, deputy state’s attorney.Isaac was born with significant medical conditions and disabilities that required the assistance of caretakers for up to 80 hours a week.