Thomas Elvin Darnell, 75, died Monday in the Montgomery County Jail, according to a statement from the sheriff's office.
The video above is from previous reporting.
Darnell was arrested at his home in Kansas on May 11 in connection with the March 1983 death of Laura Marie Purchase. Purchase's body was found burning in a Montgomery County field and wasn't positively identified until three years later.
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Authorities say DNA collected during the investigation matched Darnell to DNA found on Purchase's body.
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"Darnell has been in failing health even at the time of his arrest in May," Montgomery County Sheriff's Office representatives said Wednesday in a statement. "Darnell had numerous medical issues and was on hospice care at the time of his death."
The year Purchase was found burning in the field, before she had a name, self-professed serial killer Henry Lee Lucas confessed to the crime and was convicted three years later, the same year she was identified.
In 2007, the cold case squad at the Montgomery County Sheriff's Office resubmitted DNA found on Purchase and authorities discovered the profile of an unidentified man.
That DNA eliminated Lucas, along with his alleged co-defendant, Otis Elwood Toole, in 2008. Lucas had confessed to approximately 600 murders. Nearly 200 of those murders across the United States have been cleared. Lucas died in prison in 2001 after his death sentence was commuted to life.
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In October 2019, the MCSO Cold Case Squad sent the DNA evidence in for genealogy testing, and in April 2020, a genealogy report was completed. Meanwhile, investigators were working their own leads that showed Darnell was a potential suspect.
On March 17, 2021, 38 years later to the day that Purchase's body was found, investigators went to Kansas City and collected a DNA sample from Darnell. In April, they discovered his DNA matched the DNA found on Purchase during the autopsy.
Darnell's exact cause of death will be determined by an autopsy. The Montgomery County Sheriff's Office Homicide and Violent Crime Unit and the Texas Rangers are handling the investigation.
See more cold case investigations Courtney Fischer has delved into with 13 Unsolved.