wrongful conviction cases and says she has freed many defendants, including ryan ferguson. sandy contacted her, and she joined the case not long after "making a murderer" came out. we caught up with her at the correctional institution when she paid a visit to avery in $2016. >> million question. do you think you have new evidence that could free steven avery? >> we do, yeah. >> reporter: zellner invited "dateline" into this war room she created outside of chicago, all dedicated to the avery case. >> do we know if that was tested? >> reporter: and she even showed us this rav4 she bought to get a better understanding of teresa's vehicle. then in august of 2016, to much media fanfare, she filed a motion in manitowoc county court, featuring new testing of the evidence. >> we're going find out one way or the other was the evidence planted. >> reporter: kathleen zellner is known as an aggressive prosecutor. >> ari melber is a chief legal