Let's get started with the utah pediatrician charged with killing his ex-wife. He faces first degree murder charges in the 2011 slaying and will make his first court appearance later today. Abc's gio... See More
Let's get started with the utah pediatrician charged with killing his ex-wife. He faces first degree murder charges in the 2011 slaying and will make his first court appearance later today. Abc's gio benitez is here with that. Reporter: She was a 49-year-old biologist at the university of utah. At the height of her career. Right now the mystery, was she murdered or did she kill herself? It took 18 months for police to name the suspect. How did she end up dead in her bathtub? This morning investigators say she was murdered at the hands of her ex-husband, john brickman wall, a pediatrician. His attorney telling abc news the doctor is innocent, but always believed he'd be charged. I think deep down inside we both sort of expected this to come someday. Reporter: The couple had been ied for 15 years but divorced in 2005. A bitter custody battle over their four children followed. But in september of 2011, her body was discovered in her bathtub, a knife nearby. Blood everywhere. At first police thought she committed suicide. She was doing amazing things in her career at the time. This was just out of character for her to do this. Reporter: The autopsy report says she drowned but also mentions injuries on her body that are, quote, not typical of self-inflicted wounds. It says they could be defensive injuries from a struggle with another person. Immediately everyone pointed their finger at dr. Wall. Reporter: Police interviewed wall that day finding fresh scratches on his arms and on his face. He told the police that the scratches on his arm were from gardening and the scratch on his face, he believed occurred when his dog woke him up. Reporter: Then this, toxicology testing found an elevated level of xanax in her body. An amount that police believe could have been fatal. I don't know how someone could be forced to take those kind of drugs without there being some evidence of that. Reporter: There's a twist. The couple's son accused his own father of killing his mom. I think this was a very bold and courageous move by a young man. Reporter: Police say wall has not been able to tell them exactly where he was that morning but a friend reportedly saw him driving near the crime scene around 7:00 a.M. I don't know what to make of that. I don't think it's -- it means a whole lot either way. Reporter: But police are suspicious. Following their interview, wall allegedly told someone, "only a monster would do what was done to uta. If it was me, I don't remember." And wall's attorney calls some of the information in that arrest warrant wrong. And he believes there's not enough evidence to convict wall. Really? He'll be in court later today. He will be. Thanks, gio, very much.
This transcript has been automatically generated and may not be 100% accurate.