Family of Vegas attorney, whose death was originally ruled suicide, believes husband killed her Susan Winters had a lethal combination of oxycodone and antifreeze in her system

 -- Even in Las Vegas, a place where anything can happen, the story of attorney Susan Winters’ death is shocking.

Originally ruled a suicide, authorities have now re-opened the case as a murder investigation after seeing evidence that makes them suspect her husband was possibly involved.

Early on Jan. 3, 2015, the 48-year-old part-time judge and mother of two was rushed to the hospital from her suburban Las Vegas home after ingesting lethal combination of oxycodone and antifreeze. She died later that day.

The Clark County coroner’s office concluded after an autopsy that Winters died of a combination of ethylene glycol poisoning and oxycodone intoxication. Ethylene glycol is the main ingredient in antifreeze.

Her husband Gregory “Brent” Dennis, a 54-year-old psychologist, was arrested in early February and charged with murder in connection to her death.

The Winters family does not believe Winters killed herself, but instead they suspect Dennis is responsible for her death. They hired a retired FBI agent to investigate him, along with attorney Tony Sgro, who filed a civil suit against Dennis on the Winters’ family’s behalf before Las Vegas authorities re-opened the case as a criminal investigation.

“Everything that we learned seemed to point towards foul play,” Sgro said. “Nothing we learned tended to point toward Susan taking her own life.”

During his deposition for the civil case, Dennis said he couldn’t save Winters from her demons, and that she “was agitated and making threats to hurt herself” the day before she died.

But her family in Oklahoma is convinced there is something suspicious about Dennis’ story.

“When mom said, ‘Susan’s dead,’ I said, ‘What did he do to her?’” her brother Chris Winters told ABC News.

Srgo complied a nearly 50-page investigative report, citing potential evidence against Dennis, including an alleged substance abuse addiction and a connection to a man named Jeffrey Crosby, who in the past had been convicted of felony possession with intent to sell cocaine.

In deposition, Dennis admitted that he would pay Crosby cash and in exchange, he “would provide me substances.”

According to a police report, phone records show there were six calls and texts from Winters’ phone to Crosby’s phone in the days before she died. Her father, Dan Winters, said his daughter was calling Crosby to tell him that she was going to go to the authorities.

“She was going to turn him in and Brent in for selling to him,” Winters said. “She wanted Brent to stop and she thought that would get him [to] stop.”

Dennis disputed that in his deposition, saying he didn’t have “any recollection” of his wife saying she would turn him in.

“Honestly I don't recall any threat of that nature. She just threatened me,” he said.

But her parents, who have known Dennis for decades, are adamant that was the case, saying Winters was “going to go to the psychology board and tell them what he [Dennis] was doing.”

Richard Schonfeld, Dennis’ attorney, says Dennis’ drug problems are in the past.

Winters and Dennis’ marriage was rocky. Less than two years before Winters’ death, the couple separated for several months. Winters' parents said she was seeing a therapist for anxiety over her marital problems – problems she seemed to have kept FROM her family.

“There were things that we didn’t know,” Chris Winters said.

Schonfeld says Winters’ family is simply in denial.

“We believe that the Winters family has been unable to accept that Susan Winters’ death was a suicide,” Schonfeld said. “It was deemed suicide by the Henderson Police Department. It was deemed to be a suicide by the Clark County coroner’s office, and they were unable to accept that fact.”

Her family argues Winters had everything to live for, including two beautiful daughters and a new job helping her parents with their string of Sonic hamburger franchises. Winters owned a share in the lucrative family business, netting her roughly $200,000 a year.

Most telling, Winters’ family says, is Winters had a $1 million life insurance policy that Dennis immediately collected on after her death.

“Brent Dennis called the insurance company the first business hour of the first business day after his wife passed away,” Sgro said. “She passed away on a Saturday -- he was on the phone with the insurance company around 9:30 in the morning on Monday.”

But Schonfeld says a spouse has every right to file a life insurance claim without it being suspicious.

“I don’t think the actions when looked at in the totality of the circumstances raised any red flags whatsoever,” he said.

He also cited the children’s support of their father as evidence of Dennis’ innocence.

“Mr. Dennis has been the exclusive care provider for his children for the last two years with no issue,” Schonfeld said. “A loving, harmonious household. And he’s very supportive of his children and they’re very supportive of him. And I believe that says a lot.”

The district attorney charged him with murder, leading to the summary suspension of his license to practice psychology. He is currently out on bail. An upcoming preliminary hearing will determine if Dennis’ case goes to trial.

“Typically if you have a suicide, you have the things that the person used to kill him or herself there -- a gun, poison, pill bottles, sitting right next to the person who has died. In this case that wasn’t there and prosecutors believe that’s because this wasn’t a suicide,” said ABC News chief legal analyst Dan Abrams.

The coroner’s original cause of death could be a potential weakness for the prosecution, says Abrams. “The minute that coroner gets on the witness stand, the question is going to be, ‘Excuse me, didn’t you initially say this was a suicide?’ And that’s exactly what the defense’s argument here is.”

Dennis’ attorney says he plans to plead not guilty. His next pre-trial hearing is scheduled for August. Dennis declined ABC News' requests for an interview and deferred to his attorney.

But for the Winters’ family, the case seems clear.

“Susan held all the cards in his world. She had the girls. She had money,” said Chris Winters’ wife Julie Winters. “What do you think, what makes sense? He killed her.”

“Nevada has the death penalty but I pray he doesn’t get it. And I hope that he stays forever in jail,” Chris Winters added. “Death is too good. I’d like him to be punished for the rest of his life.”