Did the misuse of a popular eye drop medication lead to homicide?

Steve Clayton retired a millionaire in his early 40s after selling his successful physical therapy business. In 2018, Steve appeared to be enjoying the good life with his wife of five years, Lana, who worked as a nurse. The couple lived in a waterfront mansion, in Lake Wylie, South Carolina. Steve, 64, and Lana, 52, would host lavish parties for his close-knit family and their friends, often featuring live music and fireworks.

But Steve's golden years of retirement came to a crashing end on July 21, 2018 when Lana discovered him dead at the bottom of a staircase in their home. She told first responders Steve was bedridden for three days due to a bout of vertigo leading up to his death.

Almost a month later, investigators discovered a chemical — found in many over-the-counter eye drop medications — in Steve's blood, which would become the focus of their investigation.

"48 Hours" and correspondent Peter Van Sant investigate in "The Eye Drop Homicide." 

Coroner Sabrina Gast dispatched a deputy coroner who arrived at the Clayton mansion shortly after Steve's death. The coroner's office ruled Steve had most likely succumbed to a heart attack. The deputy noted nothing suspicious at the scene and reported Lana was cooperating with investigators.

"She was appropriate in answering questions. She didn't seem to be like she was hiding anything," Gast told "48 Hours."

Yet, there were things that didn't sit well with Steve's nephews Nick French and Kris Phagan. Nick, an experienced police officer in a nearby town, had rushed to the mansion shortly after Steve's death. He immediately noticed red flags: why had Lana not attempted to revive Steve and why didn't she call 911 herself? Instead she had flagged down a passing motorcyclist. Nick was also alarmed when Steve's phone — which he described as his lifeline — was nowhere to be found. And there was more.

Nick told "48 Hours" that just hours after Steve's death, Lana decided to have her husband's body cremated.

"She looked up from her hands and said, 'That funeral home, the one that's right down the street, let's take him there and have him cremated,'" Nick said.

When Steve's nephew Kris asked Lana for Steve's will to check it for his burial wishes, he says he was taken aback by Lana's response when she claimed Steve had no will. Kris told Lana he knew there was a will. His uncle had made him the executor.

"At that point, she stood up, turns and looks at me in the eye and says, 'I said there is no will,'" Kris told "48 Hours."

Kris was uncomfortable with the idea of cremation. Without letting Lana know, Kris and Nick called the coroner's office and demanded an autopsy and a toxicology test. Coroner Gast agreed.

The toxicology results revealed the presence of the tetrahydrozoline, a chemical Gast had never heard of before.

"I was like, what is tetrahydrozoline? I don't know what that is? I had to look up what tetrahyrozoline was," Gast told "48 Hours."

Tetrahydrozoline, also known as THZ, is a common ingredient that is found in numerous eye drops, including Visine.

Forensic toxicologist Demi Garvin, whose toxicology lab detected the chemical in Steve's blood, told "48 Hours" THZ can be extremely toxic and even deadly if ingested in large amounts.

"It does have that action on the heart where it reduces blood pressure, heart rate. And then it also causes breathing to slow. And if breathing slows sufficiently, it will cause respiratory depression, which then causes death," Garvin said.

Lana Clayton was brought into the coroner's office and questioned by Gast and her deputy as investigators from the York County Sheriff's Office and the FBI listened in.

Lana told Gast her husband liked to put few drops of Visine in his coffee every morning to help him go to the bathroom.

Forensic toxicologist Demi Garvin told "48 Hours" that made no sense at all and it was not something anyone would ever want to do. Users of medications like eye drops must strictly follow the manufacturer's directions.

York County sheriff's investigators took over the interview. As they pressed Lana, she got defensive and eventually stopped talking. But a few hours later, Lana spoke with a detective at her home and what she told him, say investigators, was nothing short of a confession to murder.

You can watch their exchange on Saturday night's "48 Hours."