avery in for an investigation. >> the key is in your bedroom. you know the key is it because you put the key there. that's the only way the key gets there. >> no. >> yes, steve, yes. >> a tour was defined and claimed cops were framing him, planting evidence. >> that's the way it is. >> the evidence, the cops got the evidence. >> last thunder and wiegert weren't buying. it and placed steven avery under arrest. >> we're not mad at you, okay? >> somebody is doing a good job on me. >> investigators were convinced they had their man. still, they didn't know how or why teresa had been killed. >> coming up, shackles, handcuffs, strange behavior. >> teresa is creeped out. >> could something in his past have led him to murder? when dateline continues. why hide your skin if dupixent has your moderate-to-severe eczema, or atopic dermatitis under control? hide my skin? not me.