>> reporter: under cross-examination, even brad the escort said peterson had told him how much he loved his wife. >> in his e-mails unlike most of my clients he indicated that he had a great relationship. most clients don't want to say anything about the relationship. he indicated he had a warm relationship with his wife and nothing would ever destroy that. >> reporter: michael hadn't killed kathleen, the defense argued, and he certainly didn't kill family friend, elizabeth ratliff. they called their own medical expert who reviewed her autopsy reports and said it wasn't a murder. >> is blood in all of the ventricles of the brain consistent with a stroke from natural causes? expert: it is consistent. >> reporter: then, there was the mount everest of the case: the forensics, explaining to the jury all that blood in the peterson stairwell. >> the defense would call dr. henry lee to the stand. >> reporter: the defense called celebrity forensic expert dr. henry lee, of o.j. case fame, to show the jury in theatrical fashion just how kathleen, falling, then staggering about, coughing up blood, could have accounted for the spray.