Until 2008, Hayne performed about 80 to 90 percent of criminal autopsies in Mississippi, and has testified to performing more than 1,500 autopsies per year. Performing more than 325 autopsies per year is considered a "Phase II deficiency" by the National Association of Medical Examiners, and prevents an office from being accredited. While performing these autopsies, Hayne also regularly appeared in court to testify as a forensic expert, and held down two hospital jobs.
Cory Maye case
Hayne is the medical examiner in the Cory Maye case and testified at the trial for the murder of Ron Jones. In this testimony, "Hayne said he could tell from the damage to Jones’ body the trajectory the bullet took as it entered the officer. Based on that trajectory, he speculated that Maye was standing when he shot Jones, not lying on the floor, as Maye testified. Hayne’s testimony seriously damaged Maye’s credibility with the jury. However, according to a post-trial review by an actual, board-certified forensics expert whom Maye’s new legal team hired, it would be impossible to project the bullet’s trajectory based on the tissue damage in Jones’ corpse, because Jones might have been crouching, rolling, or prone when he was hit."
Jimmie Duncan case
Jimmie Duncan was convicted for the 1993 murder of Haley Oliveaux of West Monroe, Louisiana based primarily on the testimony of Hayne and Michael West, a dentist who claimed to identify bite marks and at the time coroner of Forrest County, Mississippi. Duncan had admitted to leaving Oliveaux in a bathtub unattended, and was initially charged with negligent homicide. Hayne examined Oliveaux and claimed to have found bite marks on her face that had not been seen by any of the other medical professionals who had previously examined her body, such as EMTs and hospital personnel. After this, a mold was taken of Duncan's teeth for use in bite mark analysis by Michael West. In performing this analysis, West repeatedly pressed the mold into the cheek of Oliveaux' corpse, creating bite marks which had not previously existed. This was recorded on videotape which surfaced in 2008. Michael Bowers, deputy medical examiner for Ventura County, California commented with regard to the bite marks that "Dr. West created them. It was intentional. He's creating artificial abrasions in that video, and he's tampering with the evidence. It's criminal, regardless of what excuse he may come up with about his methods."
Tyler Edmonds case
At 2004 the trial for the murder of Joey Fulgham, in which his 13-year-old brother-in-law Tyler Edmonds was also tried and convicted, Hayne claimed to be able to determine from the bullet wounds received by Fulgham that Edmonds had also been holding the gun at the time the trigger was pulled. On appeal to the Mississippi Supreme Court this testimony was called "speculative" and "scientifically unfounded" by the court. Upon retrial in 2008, absent Hayne's testimony, Edmonds was acquitted.
