terrorizing the boston area, grabbing international headlines and the silver screen. desalvo was sentenced to life for unrelated crimes and stabbed to death in prison. thanks to new technology, authorities say they've matched dna from one of the strangler's relatives to dna preserved 49 years ago from the crime scene and victim mary sullivan. plain clothed detectives secretly detailed the desalvo relative to get that sample. source tells cnn when he threw away a plastic water bottle at a construction site they grabbed it. >> it's a fair and legal and ethical method for collecting. >> reporter: in a statement albert desalvo's family are "outraged and offended" after offering a dna sample last year. police are praised for not giving up. >> it's amazing to me today to