Husband Pleads Guilty to Killing Wife with Antifreeze, Opioids After Death Was First Ruled Suicide 

Dr. Gregory "Brent" Dennis, 59, pleaded guilty to voluntary manslaughter charges and faces three to 10 years in prison

A Nevada psychiatrist has pleaded guilty to voluntary manslaughter in the death of his wife, who he killed with antifreeze and opioids.

PEOPLE confirms that Dr. Gregory "Brent" Dennis, 59, entered a guilty plea on Tuesday, agreeing to a three- to 10-year prison sentence.

Dennis' wife, attorney Susan Winters, died in 2015. According to CBS-8, there was enough antifreeze in her system to kill her twice over. She also had a lethal amount of oxycodone in her system.

Winters' death was originally ruled a suicide. According to a police report, Dennis told first responders that he suspected that Winters had drunk antifreeze that they kept in their garage. Dennis alleged that he had found an internet search made by Susan the night before she died, seeking information about antifreeze poisoning.

But the timeline didn't add up. Investigators later deduced that the final internet searches were done at 5:15 a.m., when Winters was already unconscious and dying from the poisons.

Dennis was arrested in February 2017 and charged with one count of murder with a deadly weapon. According to the Las Vegas Review Journal, he remained free on $250,000 bail while his case worked its way through the court system.

An arrest report at the time claimed that Dennis was battling a cocaine addiction that drained his finances. He stood to inherit approximately $2 million — including a $1 million life insurance policy — upon his wife's death.

The trial was scheduled for earlier this year, but it had been delayed due to the COVID-19 pandemic.

Although he pleaded guilty, Dennis still maintains his innocence.

"Brent Dennis resolved this case without making any admission of guilt in order to eventually return his life to normalcy," defense attorney Richard Schonfeld said in a statement to the Las Vegas Sun.

Prosecutor Marc DiGiacomo also told the Sun that a possible 10-year sentence is a "reasonable outcome" in a complex case that involved circumstantial evidence.

Dennis will face sentencing in May.