then, early march, 2006, four months after teresa's death, ken kratz called another big press conference said steven avery's nephew had confessed that he and avery killed teresa together. kratz went into graphic detail, which we won't repeat here. >> there is a substantial amount of physical evidence that now makes sense. all right? that now fits a lot of pieces together. >> reporter: the prosecutor charged the nephew, 16-year-old brendan dassey, as a co-conspirator in teresa's murder. with dassey's statements, kratz began constructing a narrative. and investigators returned to the avery property once more and found this in his garage, a bullet fragment, with teresa's dna on it. >> it matched the rifle that was over steven avery's bed. >> reporter: with that, kratz had a final piece of the puzzle. steven avery's trial began in february, 2007. >> all of the evidence points to one person. >> reporter: d.a. kratz didn't call brendan dassey to the stand, but relied on the physical evidence to say what he believed happened -- steven avery lured teresa out to his property, disguising his calls