After the 2015 death of Susan Winters in her Henderson, Nevada, home, police, the district attorney and the medical examiner all initially reached the same conclusion: it was tragic, but also at her own hand.

But Susan’s parents, brother and sister-in-law never believed that the vibrant 48-year-old attorney would have taken her own life. They launched their own investigation into the Nevada mom’s death, hiring a team of private investigators and one of Las Vegas’ most respected criminal defense attorneys to dive into the mysterious case.

“We wanted justice for Susan. That was the only thing that kept us going,” Susan’s mom, Avis Winters, said in the Dateline: Secrets Uncovered episode titled “A Cool Desert Morning.” 

The family’s unrelenting quest for justice would uncover evidence that put the case in a stunning new light and ended with an arrest.

What happened to Susan Winters? 

The couple’s life together took a tragic turn the morning of Jan. 3, 2015 when Dennis made a frantic call to 911 to report his wife wasn’t breathing.

“My wife is unconscious,” he can be heard telling the dispatcher in a recording of the call. 

Once emergency responders arrived, they were able to restore a pulse and Susan was rushed to a local hospital, but the situation was grave. Susan had swelling around her brain and the prognosis wasn’t good.

Dennis called his in-laws in Oklahoma to tell them that Susan had tried to take her own life. 

“I’m pretty much frozen on the inside because I didn’t want to believe any of it,” Avis recalled.

Susan died before they ever made it to the hospital. 

Dennis claimed Susan had been researching how to kill herself

In the aftermath of the tragedy, Dennis told a Henderson Police detective that Susan was being treated for anxiety and depression. Susan had even once tried to kill herself during a brief split in 2012 during the couple’s marriage, making it seem plausible that she had committed suicide.

Dennis also laid out the couple’s last day together.

“He said that during the day they had been drinking together and that he believed that Susan was mixing her drinks with her anti-anxiety medication,” reporter Kate Briquelet, who covered the case for The Daily Beast, explained. “They had been arguing about the state of their marriage.” 

He claimed that Susan had flown into a rage and his young daughters went to an area shopping center to escape the drama. He told the detective that when he returned from picking the girls up, Susan was asleep. 

According to Dennis, after he got home, he noticed that Susan had allegedly been searching how to commit suicide with anti-freeze on her computer. Dennis told the detective that he tried to wake his wife up to talk about what he found, but she didn’t want to discuss it.

He also led the detective to two bottles of antifreeze he said he discovered in the garage after her death.

A medical examiner would determine that Susan died from a fatal dose of antifreeze and a fatal dose of oxycodone in her system. Her death was quickly ruled a suicide and Henderson Police closed the inquiry into her death.

Questions surrounding Susan’s death

But Susan’s parents, brother Chris and sister-in-law Julie never believed that Susan had taken her own life.

“Nobody in their right mind would drink that and go through that two day physical pain that it takes to die from antifreeze,” her father Danny argued. “You don’t just die immediately.”

They said in the weeks before Susan’s death she had seemed happy and was busy planning for the new year ahead. Their suspicions grew when just five days after her death, Dennis laid out Susan’s belongings and told her friends they could take whatever they wanted.

“It was like she was a piece of trash that he could discard at will,” Avis remarked.

After meeting with police and the coroner and getting nowhere, the family decided to take matters into their own hands and hired a private investigation firm. 

“We needed justice for Susan. That’s it,” Chris said. “We said all we wanted to know is the truth.”

Private investigator discovers secret life

Just days after Susan’s funeral, the PI firm placed Dennis under surveillance and they quickly learned the licensed psychologist was leading a secret double life.

They discovered that Dennis was making frequent, often daily, trips to The Orleans casino in Las Vegas where he regularly met with a man with past cocaine-related convictions. 

They gathered evidence to suggest that Dennis had been hiding a significant drug problem, but it wasn’t enough on its own to prove he’d had anything to do with Susan’s death.

Winters family hires criminal attorney

The family soon decided to ramp up their investigation and hired criminal defense attorney Tony Sgro to see whether the seasoned attorney could build a case against Dennis. 

 “We defend so many murder cases, we know what the prosecution does to put them together,” Sgro explained.

To fund the venture, the Winters dipped into their vast wealth of financial resources.The family owned more than 100 restaurant franchises including dozens of Sonic Drive-Ins. 

With Sgro’s help, the family learned that just days after Susan’s death, Dennis deposited a $180,000 check from an account only Susan had access to into the couple’s joint account, which he now had sole control over. They didn’t believe the check had been written by Susan.

They also learned that Susan had a $1 million life insurance policy that listed Dennis as a beneficiary and that he had called the company the first day they were open after her death to make the claim.

Dennis also gained control of Susan’s shares in her family’s restaurant business. The Winters — who were unwilling to do business with their former son-in-law — bought back the shares for approximately $700,000. 

“We wanted him gone at that point,” Danny said of the family’s decision.

The Winters File Civil Suit Against Brent Dennis

The family had established that Dennis had a significant financial motive to want Susan dead, but In an effort to gather even more evidence against him, they sued him in civil court for Susan’s wrongful death. The move allowed Sgro to be able subpoena information like banking records and cell phone reports and schedule depositions with Dennis and others close to the case.

The night Susan lay dying, Dennis had insisted that he had been home all night asleep next to his wife. But phone records showed that Dennis had made a trek in the early morning hours to The Orleans hotel to meet up with his drug dealer. 

During his deposition, Dennis admitted to using controlled substances and said his wife had “made threats” to turn him in—putting his psychologist license in jeopardy—but he insisted he’d never taken the threats seriously. He also claimed that the family was planning to use that $180,000 as a down payment for a new home and alleged that he and Susan had written the check out together. 

In their own depositions, the couple’s daughters testified that they fully supported their father and believed that their mother had committed suicide after battling depression for years.

After the deposition, which Sgro said Dennis was “stuttering and stammering” his way through, the Winters family felt they had enough evidence to bring to Clark County prosecutor Marc DiGiacomo.

Clark County Prosecutor Reopens the Case

DiGiacomo agreed to reopen the case, alongside Henderson Police, in the summer of 2016 — and it didn’t take him long to reach the same conclusion as the Winters’ family.

Although Dennis had insisted the couple was happy before her death, a search warrant issued for Dennis’ phone revealed he’d recorded arguments the couple had before Susan’s death.

“I just don’t want to go into my 50s with somebody who hates me as much as you do,” she told him in one heated exchange.

DiGiacomo described the couple’s relationship as “very dysfunctional.” 

“It is fairly clear that her and Brent’s relationship is at the breaking point,” he said.

Authorities also learned that Dennis called to check on the balance in Susan’s exclusive account hours before her death, suggesting he knew she was going to die and was already planning to take out the money before her parents could freeze the accounts.

After consulting with a toxicologist, who examined Susan’s death, DiGiacomo theorized that Dennis tried to poison his wife with antifreeze, but when that was taking too long to take effect, he drove to meet his drug dealer to obtain a fatal dose of oxycodone, which he somehow got his ailing wife to consume.

Authorities noted that Susan did not have a prescription for oxycodone and no bottle of it was ever found at the scene.

Dennis was arrested in February of 2017 and charged him with murder.

The case continued to drag out for years and was delayed by the COVID pandemic, but Dennis eventually agreed to enter an Alford plea, which does not admit guilt but acknowledges prosecutors have enough evidence to achieve a guilty verdict, to voluntary manslaughter. 

Dennis was sentenced in May of 2022 to three to 10 years behind bars.

A civil court also found him liable for Susan’s death in 2023. Dennis was ordered to pay the Winters family just over $1 million.

While it was some measure of justice, for the Winters family, it will never be enough.

“For me to think about my daughter laying there, going through that with the antifreeze, oxycodone, whatever else he put in her body, there ought to be a special place in hell for him and I hope he goes there,” Danny said.