Richard and Nancy Lyon
The cause of death was initially attributed to septic shock, a catch-all name for a condition that occurs when a bacterial infection overwhelms the body, reducing blood flow and causing failure of vital organs.
But when an autopsy showed Nancy had 100 times the normal level of arsenic in her body, the Dillard family aggressively pressed for a criminal investigation by authorities in both Dallas and University Park, the suburb where the death occurred.
The unwitting Richard, meanwhile, jetted off with Tami Lyn Gaisford for a Mexican holiday nine days after he buried his wife.
They returned to find police detectives eager to speak with them. Cops discovered that Richard's orders for poison purchases at the laboratory supply store near Houston had included arsenic and other toxic substances.
Richard insisted he was innocent and pointed police toward three other suspects: Bill Jr., with whom Nancy had had the incestuous relationship; a colleague at Trammell Crow with whom Nancy had a testy relationship, and Nancy herself, trying to attract Richard's sympathy. Richard said any poison he may have purchased was used to eradicate the fire ants, not his wife.
Trying to smoke out information, police called a press conference on March 20 to announce that they believed the death of Nancy Lyon to be a murder by arsenic poisoning. The next day, police named Richard Lyon as the possible culprit.
"He is the primary suspect in the case," said a police spokeswoman. "There is no doubt about it."
Lyon and his attorney, Ron Guthrie, responded on March 22 with a press conference of their own, at which they named Bill Jr., the coworker and Nancy as possible responsible parties.
Reporter Megan Doren began her story in the Dallas Morning News, "Richard Lyon on Friday calmly and sadly denied giving his wife the arsenic that killed her."
But the authorities were unconvinced by Richard's claims of innocence and sleuthing theories.
On May 16, 1990, three months and two days after Nancy Lyon's death, he was arrested and charged with murdering his wife by methodical poisoning. He was set free on $50,000 bail.