he learned teresa halbach had an appointment on october 31st. >> this is teresa with "auto trader" magazine. just giving you a call to let you know that i can come out here today, in the afternoon. it will be around 2:00. >> reporter: steven avery confirmed to investigators that teresa had been on the property that day and left around 2:00 p.m. avery didn't tell them much more. but for investigators, a dark tale started emerging from the physical evidence, especially when they made a gruesome discovery in the back of teresa's suv. >> we find teresa's blood in the vehicle, primarily in the cargo area of the rav-4. >> and in the front, more blood. >> there was blood on some of the upholstery and a very telling swipe of blood near the ignition switch of the vehicle. >> tests showed that blood was steven avery's, taking him from person of interest to prime suspect. you believe you can explain the blood from steven avery? >> well, yes, absolutely. steven avery had a cut on his right hand, middle finger that was freshly scabbed over. if you took that key and put it in that ignition switch, it lin