. >> reporter: otto hanak tried to confirm the testimony from sebesta's jailhouse witnesses. >> we can't find anybody that can positively say, in court or in this room, that "i heard anthony graves say this, i heard robert carter say this." >> reporter: he looked into roy reuter's knife. >> the blade is flimsy. >> reporter: and, according to hanak, a knife this flimsy could not have caused the kind of wounds to the skulls that were found on some victims. >> i personally do not believe that that blade is strong enough, nor is this knife made well enough to go through human skulls. >> it's a switchblade knife. they're made pretty sturdy. >> reporter: d.a. charles sebesta had argued graves' identical knife had inflicted 66 stab wounds the night of the murder. >> there's no doubt that that knife could have survived that. we had texas ranger testimony that it could have done it. >> reporter: but hanak, who is a

>> reporter: siegler and her investigator, otto hanak, soon realized nicole and her students were right on target. >> every single time we would reinvestigate or re-talk to a witness that they had talked to, we would find that they were right. >> reporter: one by one, the pillars of the prosecution's case crumbled. >> we tried to find paperwork, people, anything that we could-- especially a motive-- to say anthony graves committed the capital murder with robert carter, and we found nothing. >> reporter: otto hanak tried to confirm the testimony from sebesta's jailhouse witnesses. >> we can't find anybody that can positively say, in court or in this room, that "i heard anthony graves say this, i heard robert carter say this." >> reporter: he looked into roy reuter's knife. >> the blade is flimsy. >> reporter: and, according to hanak, a knife this flimsy could not have caused the kind of wounds to the skulls that were found on some victims. >> i personally do not believe that that blade is strong enough, nor is this knife made well enough to go through human skulls. >> it's a switchblade

>> reporter: siegler and her investigator, otto hanak, soon realized nicole and her students were right on target. >> every single time we would reinvestigate or re-talk to a witness that they had talked to, we would find that they were right. >> reporter: one by one, the pillars of the prosecution's case crumbled. >> we tried to find paperwork, people, anything that we could-- especially a motive-- to say anthony graves committed the capital murder with robert carter, and we found nothing. >> reporter: otto hanak tried to confirm the testimony from sebesta's jailhouse witnesses. >> we can't find anybody that can positively say, in court or in this room, that "i heard anthony graves say this, i heard robert carter say this." >> reporter: he looked into roy reuter's knife. >> the blade is flimsy. >> reporter: and, according to hanak, a knife this flimsy could not have caused the kind of wounds to the skulls that were found on some victims. >> i personally do not believe that that blade is strong enough, nor is this knife made well enough to go through human skulls. >> it's a switchblade