>> dave pietz isn't the first guy to step out on his spouse. all of you certainly know people that have done that. have they killed their wives or husbands or anything like that? >> and the defense countered that if anyone had secrets to hide, it wasn't dave. it was nikki. >> there's another side to all this. >> the defense now turned the focus to nicole pietz, and in the last few weeks of her life. >> raise your right hand. >> lawyers called to the stand their main witness, nikki's doctor, carole. she had been her primary physician for five years. >> you knew nikki's history, did she have trouble as a young woman? >> i did. >> and been in rehab at one point? >> and we had talked about it throughout her care with me. >> so when nikki came into the office complaining of severe back pain at the end of 2005, the doctor said she had nikki's past addiction in mind. the doctor testified that she did put nikki on pain