dr. mike dixon's door. dr. mike dixon's door. >> dr. dixon? i'm detective johnson with the lubbock police department. >> reporter: but why wouldn't he have shared all that with police who were then coming by his didn't know what to do and he's like, okay. "let's not bring dave in 'cause then we're like throwing dave under the bus." plus it looks bad for him. i was trying to get pictures about this guy that was dating his former girlfriend. i didn't mean to kill dr. sonnier. i have nothing against dr. sonnier or his family, or richelle shetina. i have nothing against any of them. i really don't. >> reporter: what would you say to them right now if they were watching? >> i'd tell them that i'm very sorry. i took your loved one. >> reporter: despite shepard's send undeterred. and a year after the mistrial, mike dixon faces a retrial. >> amarillo doctor michael dixon is back on trial -- >> reporter: and this time around, matt powell has a new witness. >> the number one most important thing from this second trial was the unbelievably courageous tes

dr. mike dixon. his name is dr. thomas michael dixon. he's a plastic surgeon in amarillo. >> he was richelle's old boyfriend. a well-to-do and well known plastic surgeon with a beautfiul home, a show. >> i get the patients that come in and say, "i want to look like j.lo or beyonce." >> mike was married with three kids when he first met richelle at a spa he owned. he started seeing her on the side and when his wife found out, she divorced him. mike and richelle dated for about a year and a half. but she says it wasn't always easy. >> it was volatile. it was up and down and he would -- i believe that he was >> but the final straw was a birthday gift that fell flat. >> he had signed me up for tea of the month and he had it mailed to me and i was just like, "really?" you know you couldn't even hand me something. you had it mailed to me? >> by all accounts she broke dr. dixon's heart when she dumped him. and she says that he begged her to come back even after she started dating dr. sonnier. with this in mind, police went to dr. dixon's home i