But he didn't have cancer. He had a mistress, and a plan to kill his wife.
"Investigators believe this was part of Martin's plan to deflect attention away from him and to later remove himself from the events that would unfold" on the day his 50-year-old wife Michele died, court documents said.
Just before her death in 2007, MacNeill convinced the former beauty queen to undergo plastic surgery. When she returned home, he drugged her and left her to die in a bathtub, where she was found by their 6-year-old daughter Ada, authorities said.
On Sunday, nearly a decade after the killing, 61-year-old MacNeill was found unresponsive and declared dead at the Olympus Facility at the Utah State Prison in Draper, where he was doing time for his 2014 conviction of first-degree murder, second-degree obstruction of justice and second-degree forcible sex abuse.
Prison officials said in a statement that MacNeill's death is being investigated, though there were "no obvious signs of foul play." His first parole hearing had been scheduled for 2052.
His attorney, Randy Spencer, told the Deseret News that MacNeill at attempted suicide at least once before while incarcerated. "I feared this day would come," he said. "It hasn't been officially released, but I suspect that that is what has happened."
Last month, the Utah Court of Appeals turned down MacNeill's bid for a new murder trial, a case that garnered national attention as salacious details of the wealthy doctor's life emerged, including accounts of mistresses and falsifying transcripts to get into both medical school and law school.
Prosecutors said he killed his wife because he wanted to be with his latest young mistress, a nurse named Gypsy Willis, who moved into the home after the murder under the pretense of being a nanny. MacNeill soon named Willis as his beneficiary.
MacNeil told so many lies over the years and was so good at deception that the chief investigator of the Utah County Attorney's Office compared his life to the movie "Catch Me If You Can," telling the Deseret News that the movie "paled in comparison."
A month after his wife's death, MacNeill abused an adult daughter, who testified that she woke up at her parent's house "to find her father rubbing her buttocks and licking and kissing one of her hands," the Salt Lake Tribune reported. Years passed, but he was eventually convicted of that crime.
Two years after the murder, MacNeill and Willis were sent to prison after being convicted of multiple accounts fraud for using one of "MacNeill's adopted daughter's social security number to open bank accounts under a false name in order to escape bad credit," ABC News reported.
But it wasn't until 2012 - five years after his wife's death - that MacNeill was charged with her murder. He was also charged with obstructing the investigation into her death, largely due to his behavior on that day of the incident.
Investigators said that MacNeill called 911 after his daughter found her in the tub, "but he lied to the dispatcher about performing resuscitation and lied to police about events surrounding her death in an effort to hinder, delay or prevent any investigation, according to the charges," the Salt Lake Tribune reported.
The dispatcher, Heidi Peterson, testified that MacNeill yelled so loud over the phone that she couldn't tell what he needed help with or where to send an ambulance. He also gave an incorrect address, she testified.
Scott VanWagoner, the emergency room physician who attended to Michelle MacNeill, testified in Provo's 4th District Court that Martin MacNeill "offered me $10,000 to continue my resuscitation and not quit."
At the time, he didn't understand why. "I think she was dead by the time she arrived at our door," he testified.
Investigators said Martin MacNeill also provided misleading information to the state medical examiner. After an autopsy in 2007, her manner of death was ruled "natural," the result of "chronic hypertension and damage to the heart muscle. But a report issued in 2010 noted "the combined effects of heart disease and drug toxicity," and said the manner of death was "undetermined," the Salt Lake Tribune reported.
After MacNeill's conviction, 4th District Judge Derek Pullan sentenced him to 15 years to life for murder as well as 15 years on the obstruction charge.
MacNeill did not speak during the sentencing.
"Mr. MacNeill, as you deprived Michele MacNeill of her life, the state of Utah exacts from you today the liberty that you otherwise might have enjoyed in your remaining years," the judge said.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)