do you think you have new evidence that could free steven avery? >> we do. >>> welcome to "dateline." it's an extraordinary case that defies easy answers. at the center of it all, steven avery. he and his teenaged nephew were convicted in the brutal murder of theresa malbook, then investigators forced to fight back. two sides. one truth. who will you believe? >> reporter: the mystery of what happened here in the sprawling fields of rural wisconsin captivated the country. >> we the jury find the defendant steven a. avery guilty. >> reporter: in 2016, convincing many both convicted of murder railroaded by law enforcement. it's a case "dateline" has been following for more than a decade as their lawyers worked tirelessly to free them from prison, we pose the questions everyone's been asking, to do men who help put avery and dassey behind bars. >> why would steven avery do this? >> a great question. >> we speak with ken kratz who has writ an book revealing his provocative theory, that steven avery made himself a murderer. >> steven avery started plannin