Was Susan Winters' death a murder? Details explored ahead of Dateline: Secrets Uncovered on Oxygen

Susan Winters, a Nevada attorney, was found unresponsive at her Henderson home on January 3, 2015. Her husband, Dr. Gregory “Brent” Dennis, a psychologist, claimed she attempted suicide using a mix of antifreeze and opioids. Initial investigations ruled her death a suicide, citing ethylene glycol poisoning and opioid intoxication, according to the Las Vegas Review-Journal's report on May 10, 2022.

However, Winters’ parents suspected foul play, prompting private investigators to uncover discrepancies. They found that Dennis had searched for information on antifreeze poisoning and had withdrawn funds from Winters’ accounts before her death, as reported in Oxygen on April 29, 2023.

Further scrutiny unveiled Dennis’ financial troubles and a history of drug use. A reopened case led to his arrest for murder in 2017. In 2022, he pleaded guilty to voluntary manslaughter and was sentenced to three to ten years in prison, according to a January 2022 report by People magazine.

Susan Winters’ case will be revisited in Dateline: Secrets Uncovered, which will air on Oxygen on February 26, 2025, at 8 pm ET.

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Susan Winters was discovered deceased with a lethal concentration of oxycodone and antifreeze in her system

The circumstances surrounding Susan Winters’ death initially led authorities to classify it as a suicide. However, subsequent investigations raised questions about whether her husband, Dr. Gregory "Brent" Dennis, was responsible for her poisoning.

Winters, a 48-year-old attorney, was found unresponsive at her Henderson, Nevada, home on January 3, 2015, with high levels of oxycodone and ethylene glycol, the main ingredient in antifreeze, in her system.

Dennis, a psychologist, told police he believed his wife ingested antifreeze after searching online for information on antifreeze poisoning, as reported by the Daily Mail on January 5, 2022. Initially, the Clark County Coroner’s Office ruled Susan Winters’ death a suicide, citing opioid intoxication and ethylene glycol poisoning.

Dennis informed authorities that Winters had struggled with depression and had spoken about wanting to end her life, per Oxygen's April 2023 report. His daughters supported his claims, stating their mother had been in emotional distress.

However, Winters’ parents were not convinced. They believed their daughter would not take her own life and decided to hire private investigators to delve deeper into the case, as noted in People magazine on January 5, 2022. That’s when things began to unravel. Investigators discovered inconsistencies in Dennis’ statements.

Initially, he claimed he had no idea there was antifreeze in the house. Later, he directed officers to bottles stored in the garage. Another red flag came from forensic analysis, which revealed that the internet searches about antifreeze poisoning were conducted at 5.15 am, a time when Winters was already unconscious. This directly contradicted Dennis’ account that she had looked it up herself, according to the Daily Mail.

The deeper the investigators dug, the more suspicious things became. There was also a financial angle: Dennis was set to receive $1 million from Winters’ life insurance and had withdrawn $180,000 from her personal bank account shortly after her death. Furthermore, he was buried in debt due to a long-standing cocaine addiction.

Private investigators tracked Dennis and found he was frequenting areas known for drug activity. Surveillance footage captured him making repeated visits to the Orleans Hotel and Casino, where he met with a known drug trafficker mentioned in the Las Vegas Review-Journal.

Brent Dennis was buried in debt due to a long-standing cocaine addiction (Representative Image via Getty)

As the evidence against Dennis mounted, Susan Winters’ parents took legal action by filing a wrongful death lawsuit. Their persistence paid off—the case was officially reopened in 2016. A year later, in February 2017, Dennis was arrested and charged with murder. However, the legal process was drawn out due to delays caused by the COVID-19 pandemic.

In 2022, Dennis took an Alford plea, meaning he did not admit guilt but acknowledged that prosecutors had sufficient evidence to convict him. He was sentenced to three to ten years in prison and will be eligible for parole in May 2025, according to People.com.

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Dateline: Secrets Uncovered is set to revisit the case on February 26, 2025, shedding light on how Susan Winters’ death, initially ruled a suicide, evolved into a full-scale homicide investigation that concluded with Dennis’ conviction. Stay tuned for more updates.