Dr. Joseph Sonnier, a pathologist residing in Lubbock, Texas, was found murdered in his home on July 11, 2012. He had been shot five times with a .25-caliber handgun and stabbed 11 times with a screwdriver. The investigation revealed that Sonnier was in a romantic relationship with Richelle Shetina, who had previously been involved in an extramarital affair with Dr. Thomas Michael 'Mike' Dixon, a plastic surgeon in Amarillo, Texas. Unwilling to accept the end of his relationship with Shetina, Dixon allegedly harbored deep jealousy toward Sonnier. Dixon recruited his friend David Neil Shepard to spy on and disrupt Sonnier's relationship with Shetina, eventually hiring Shepard to murder Sonnier in exchange for three bars of silver worth $9,000. Shepard carried out the killing on July 10, 2012. Following a tip from Shepard's acquaintance, police arrested both Shepard and Dixon. Shepard pleaded no contest and received a life sentence, while Dixon was tried twice, resulting in a mistrial before his conviction for capital murder. After a complex appellate history involving overturned convictions and reinstated life sentences, Dixon remains incarcerated while maintaining his innocence.
Country: United States
State/Province: Texas, United States
City/Region: Lubbock
Incident Type: Murder
Relationship Status: Love triangle
Relationship Duration: 1 year
Incident Date: July 10, 2012
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How the relationship or connection began.
1 year
Important relationship phases recorded for this case.
Reported red flags or early concern points.
Contributing factors and possible motives from the available sources.
2012-07-10
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Dr. Grande · Original language: English
'Romantically Active' Physicians Find Themselves in Lethal Love Triangle | Mike Dixon Case Analysis
Romantic Triangle
The case fits a classic romantic rival elimination pattern exacerbated by obsessed rejection and indirect contract enforcement. After Richelle Shetina ended her affair with Dr. Mike Dixon and began a fulfilling relationship with Dr. Joseph Sonnier, Dixon developed an intense obsession with winning her back. Initially attempting covert sabotage, stalking, and reputation destruction through a proxy (David Shepard), Dixon escalated to direct violence when subtle interference failed, using financial reward (silver bullion) to solicit Sonnier's murder.
Lubbock Police initially verified Dixon's personal alibi, which briefly directed focus away from him until a tip from Paul Reynolds identified David Shepard. Shepard provided details leading to the recovery of the murder weapon in a lake and three silver bars given as payment. Digital forensics recovered text messages between Dixon and Shepard despite Dixon's attempts to destroy his phone by jumping into a pool and removing the SIM card. Legal proceedings included Shepard's plea bargain, Dixon's 2014 mistrial due to Shepard's changed testimony, Dixon's 2015 conviction, subsequent appellate reversals, and eventual reinstatement of his life sentence for capital murder via remuneration.
Initial confusion arose when Dixon provided a verified physical alibi for the night of the murder, causing investigators to temporarily rule him out. Further complexity occurred at trial when Shepard recanted his confession, claiming the killing was an accidental discharge during a confrontation over taking photos to prove Sonnier's alleged infidelity.
Dixon recruited Shepard to monitor and sabotage Sonnier's relationship with Shetina. When harassment failed to separate the couple, Dixon provided Shepard with his .25-caliber pistol and silver bullion. On July 10, 2012, Shepard waited at Sonnier's house, shot Sonnier through an open window, chased him into the garage, stabbed him 11 times with a screwdriver, and used a modified plastic bottle as an improvised silencer, before discarding the gun in a lake.
Extremely high risk driven by persistent obsession, refusal to accept romantic separation, covert surveillance, and third-party solicitation. Dixon's behavior demonstrated extreme boundary violations including assigning a third party to stalk, photograph, and harass his ex-partner and her new boyfriend, ultimately procuring a firearm and paying for a targeted hit.
Escalating stalking behavior and proxy harassment in romantic rivalries serve as major warning indicators for severe violent escalation. Physical alibis can obscure mastermind involvement in murder-for-hire schemes, requiring aggressive digital forensic extraction and financial tracing.
Dixon sent harassing communications to Shetina, complaining about selling his family down the river for her, while unusual stalking incidents occurred around Sonnier's home, gym, and mail.
A tip from Paul Reynolds revealed Shepard's self-incriminating statements, which led directly to the recovery of the murder weapon from a lake and silver bars traded for cash.
Digital forensic recovery of 37 text messages and four calls on the day of the murder, recovered text messages from Dixon's computer sync after he attempted phone destruction, three silver bars valued at $9,000, and the murder weapon retrieved from the lake.
Richelle Shetina described Dixon's persistent romantic pursuit and prior stalking incidents. Landscapers and a co-worker described finding a broken window and spent shell casing before discovering Sonnier's body in the garage.
Follow-up investigation shifted focus from Dixon's direct physical presence to a murder-for-hire plot after Shepard's roommate came forward, leading to joint arrests and physical evidence recovery.
Dixon continues to maintain his innocence, claiming his interactions with Shepard were solely intended to document Sonnier's alleged unfaithfulness rather than commit murder.