that she's the best parts of me. >> reporter: the prosecution had the burden of proving the charges. first-degree murder and nonconsensual termination of a pregnancy. what did you think your strongest fact was going forward? strongest part of your story? >> probably the most important single piece of evidence was the shotgun. >> reporter: ballistics showed the mosberg .12 gauge was the weapon and only he had access to it that morning, prosecutors argued. >> no murderer who wants to kill lisa techel comes to the more scene without the murder weapon. >> we argued the impossibility of his story. some unknown assailant breaks in and kills the wife, that he says he's going to leave. >> reporter: prosecutors called one of seth's young friends to show the jury, they said, just how deceptive and manipulative