Doctor accused of hiring hit man to kill ex's new boyfriend goes on trial: Part 6

Dixon allegedly paid Shepard with three silver bars and a box of cigars to carry out the murder of Sonnier.
6:43 | 03/09/19

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Transcript for Doctor accused of hiring hit man to kill ex's new boyfriend goes on trial: Part 6
feel that fall chill starting to roll into Texas, but in the Lubbock county courthouse things are starting to heat up. Anything to say Dr. Dixon? This is likely one of the biggest murder trials that this city has seen in a long, long time. The gallery was packed. Everybody was there to see how this trial was going to go. Dr. Mike Dixon. Accused of hired a hit man. Friend and business partner. This case is nothing short or surreal. First you have the victim, Dr. Joseph Sonnier, a very prominent pathologist. Then you have another prominent physician, Dr. Mike Dixon and he's accused of placing a hit on Dr. Sonnier. In the middle of all of it you have a beautiful blonde named Richelle shetina. Going after someone I loved would hurt me and that's what he was going to do. He wanted to hurt me as badly as he could. I think Mike Dixon had an obsession with Richelle shetina based on the evidence. I don't think there's any doubt about that and ultimately that cost Dr. Sonnier his life. I promise I will be totally compliant, won't cause any problems. Dave Shepard is sort of the oddball friend of Dr. Dixon, and he tells police that Mike Dixon paid him in advance to do the hit. He wanted him hurt and then it gradually developed into having him killed. I think Mike Dixon controlled the situation. I think David Shepard was the perfect Patsy. I think he loved the lifestyle that Dr. Dixon could give him. I think he likes the expensive cigars and expensive scotch and everything else that came with being a buddy of Mike Dixon. Many people make the argument that Mike Dixon never laid a hand on Dr. Sonnier. He's just controlling the knife. Dave Shepard's just another instrument for Mike Dixon. What was your mindset going into that trial? Let's go Get these guys. We knew they had the right guys. In my mind, there was no other possibility. There's always two sides to these kinds of cases. And on the other side, you have Andrew Dixon, Mike Dixon's son, who has a very different view of this case. He, was a good dad. He did dad things, you know? Kind of American dream kind of stuff. Go camp and hike and play baseball and football and all those things. They're trying to prove him guilty, Ya know, and he's fighting for his life. I mean it's just terrifying and so sickening. I've known Mike Dixon for 25 years. He's as solid as they come. There was no intent to kill. I know that with all my heart. He's harmless. But in courtroom 72 of the Lubbock county courthouse, the prosecution paints a far different picture of Mike Dixon. Somebody who was arrogant. Somebody using Shepard as a pawn to keep up with Richelle and Dr. Sonnier's relationship and goodness knows what else. This is the oldest story in the book. This is vengeance. This is revenge. This is pride. One of the biggest pieces of evidence that Lubbock prosecutors used against Dixon was this .22 caliber pistol which David Shepard told police that he used to shoot Dr. Sonnier. Prosecutors presented evidence that the gun that was used to kill Dr. Sonnier was given to him by doctor Dixon. Circumstantial evidence, pretty strong stuff. David shepherd tells us that he told Dixon, "I don't have a and Dixon says, "Don't worry about that, I have that covered. I have the gun." He says, "It belongs to my brother. He gave it to me and it's clean." Police divers were seen pulling something from the lake, shepherd was on hand to point police to areas in the lake to search. He said he'd thrown the gun into a lake in Amarillo behind Dr. Dixon's office. Also, prosecutors have a wealth of text messages between Shepard and Dixon when Shepard was stalking shetina and Sonnier. When he was arrested, the swat guys told me he had actually jumped into a swimming pool and tried to ruin the phone. The problem was the man had plugged the phone in and backed it up to his computer. So all of the stuff that he thought was not going to get him in trouble was backed up to his computer. Prosecutors here are saying that they found text messages from Dixon to Shepard urging Shepard to kill. We're talking text messages like "Go get ??em," "Whip and spur," "Get R done," and "Put it on him." If you look at the text messages, "Put it on him," you know those types of things. There wasn't any doubt in my mind, you know, what they were talking about. A real eyebrow raiser is how the payoff supposedly happened to the alleged hit man here. Three silver bars and a box of cigars. It's hard to find a good Cuban cigar but the silver bars are worth some $9,000. According to prosecutors one of which was sold to this pawn shop in Amarillo, Texas before the murder and two after the murder sold by none other than Dave Shepard. What was he like? Do you remember any of his affect? He was a pretty good size guy. He seemed just like a normal guy to me. I didn't notice anything different about him. In terms of demeanor he didn't strike you in one way or another it sounds like? No, not at all. So he sold you something just like this. It's heavy. Yeah, very similar. He leaves. A couple days later he is on the front page of the paper. Right, yeah it was. I was pretty much in shock. I mean, I was blown away. All the evidence the prosecutors have against Mike Dixon is strong but their primary piece of their case is Dave Shepard. He pleaded guilty for a life sentence with no opportunity for parole. And so after the death penalty was taken off the table, that's when Dave Shepard agreed to testify against his old drinking buddy, Mike Dixon. It seemed like a slam dunk for prosecutors. They had the man who admitted to killing Dr. Joseph Sonnier as a witness. He had a chance to get up there, confirm his story, point to that guy as the person who paid him to kill my dad, and end it all. But what he ends up doing is an absolutely shock to the prosecutors and to the family of the victim. The star witness was about to blow up in the prosecution's

This transcript has been automatically generated and may not be 100% accurate.

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