having sex. reporter: the hookup never happened, but combine that with the other combustibles in the couple s life, the prosecution said, and you have all the ingredients for a fatal confrontation. it got out of control, and michael peterson snapped. and he was the only one who could have done it, according to the prosecution. reporter: further evidence that michael attacked kathleen ferociously, the prosecution stated, was as clear as the spray of blood up the staircase walls. the amount of blood, the positioning of the blood, the location of the blood, it was overwhelming. in general terms, the greater the force, the smaller the drop. reporter: to take the jury vividly up the back stairs, the prosecution called the state s blood pattern expert, duane deaver. he told the jury with certainty that kathleen peterson had been beaten to death. he testified the droplet pattern high up the walls was just what you d expect to see with a weapon rising, striking, and casting off b
lay, but high up along the staircase walls, too. too much blood, she thought, for a slip and fall. if you fell down the stairs, why would there be blood splurted up the side of the walls? it didn t make any sense to me. reporter: and she says there were household details out of order: like the table that liz set out every night with the girls breakfast plates. it was bare. the snow boots she routinely left by the front door, still on her feet. liz never wore her boots in the house. she d always took her boots off. and that was another clue to me that something was wrong. it s obvious that she was either running from someone or trying to escape. reporter: amybeth thought a full-fledged investigation would ensue. but, as she tells it, michael peterson spoke to the authorities that day, relating that elizabeth had a hereditary bleeding disorder. perhaps she d had a stroke and fallen down the stairs. the questions amybeth expected to be asked never were.