A judge has ruled that a Vermont man who was 17 when he and a friend killed a pair of married Dartmouth College professors 25 years ago will have a chance at parole in about 20 years, when he reaches the age of one of his victims. Lawyers for Robert Tulloch and the prosecution reached an agreement on the terms, avoiding a three-day planned resentencing hearing that was to begin Monday. Tulloch was automatically sentenced to life without parole after pleading guilty to first-degree murder in the 2001 stabbing deaths of Half and Susanne Zantop. But the U.S. Supreme Court ruled in 2012 that mandatory sentences of life without parole are unconstitutional for juveniles, and later applied that decision retroactively.