Two bottles of outdated antifreeze could play a key role in the upcoming murder trial of a local psychologist.

Homicide charges were leveled earlier this year against  Dr. Gregory “Brent” Dennis in connection with the 2015 death of his wife Susan Winters, a local attorney. The death was originally ruled a suicide but that changed after the Winters family hired its own private investigators.

When she died in Jan. 2015, there was enough in Susan Winters’ system to kill her twice over. She had a lethal amount of oxycodone in her system, and a deadly dose of a chemical from antifreeze. Alone, either one would have killed her. Together, there was no doubt, though it took many hours for her to die.

But how did they get into her body in the first place? No pills or antifreeze were found with her body. Her family always suspected her husband did it, and now prosecutors are zeroing in on several mysteries regarding the antifreeze.

Dr. Brent Dennis no longer practices psychology in a Boulder City building. The office is now for rent. His license was suspended earlier this year after he was charged with the murder of his wife,attorney Susan Winters.

Susan’s parents never bought the initial story that her death was a suicide. They always sensed that Dennis was responsible for her death.

“Just that he killed her. We don’t know exactly how but he gave her that antifreeze,” said Dan Winters, Susan’s father.

The Winters’ family hired a law firm to investigate the death. That led to a detailed private report which outlined numerous discrepancies as told by the grieving husband, including various accounts about the antifreeze.

In a sworn deposition, Dennis had trouble sticking to his story.

Anthony Sgro, Winters’ attorney: “If I understand it correctly, you didn’t even know you had antifreeze in the home, is that fair?”

Brent Dennis: “Correct.”

Anthony Sgro: “Do you remember where you found the antifreeze?”

Brent Dennis: “Sitting by the shelf on the floor.”

Anthony Sgro: “Okay, why, if you found the antifreeze on the floor of the garage, right, when you first located, why did you put it back on the shelf?

Brent Dennis: “I’m not sure of you saying I located it. Again, I have no clarity as far as who, you know, there were multiple people in the house.”

How did anti-freeze get into Susan’s stomach? By all accounts, she went to bed early. Evidence revealed she ingested what would have been a fatal amount of oxycodone, though she had no prescription for it. Winters family attorney Tony Sgro says Susan would have been unconscious and immobile.

“She’s surely not walking out to the garage to chug antifreeze and then put it neatly back on the shelf,” Sgro said.

Brent Dennis initially told Henderson Police he didn’t know there was any antifreeze in the house but hours later showed them some bottles in the garage. Police took photos but the bottles were not taken into evidence and were gone by the time murder charges were filed a year later.

Dennis denied buying them. The previous tenant says the garage had been cleaned out. The particular bottles couldn’t be purchased at a store because one was manufactured in 1997, the other in 2007. That’s a key point because, by law, the formula for antifreeze was changed in 2013 in order to cut down on accidental poisonings. Previously, antifreeze had a sweet taste, meaning it could be consumed in food or drink without being noticed.

“If I asked you right now what does antifreeze taste like, you would have no idea,” Sgro said.

Sgro says that one day after Susan died, Brent Dennis made an odd remark to a friend.

”’You know, Susan drank something sweet.’ Now how in the world would you conclude that she drank something sweet? He didn’t say to his buddy she drank antifreeze,” Sgro said.

How and where someone obtained two bottles of the old, sweet antifreeze will be key questions in the murder trial, and so will the various statements made by Brent Dennis, such as the first call he made to Susan’s parents.

“He said, ‘My God Dan, she drank antifreeze,'” Dan Winters said.

According to the arrest report, Brent Dennis told first responders he suspected Susan had ingested antifreeze because he’d found a page of Internet searches, supposedly made by Susan the night before, seeking information about antifreeze poisoning.

Police took a photo of the search list. But months later, investigators learned the last of the searches was done at 5:15 a.m., a time when Susan was out cold and nearly dead. Ninety minutes after the last computer search, Brent Dennis called 9-1-1.

“He waited from 5:15 until 6:45 because he wanted her heart to stop. He was standing over his wife as she took her last breath,” Sgro said.

When it became known months later that investigators had learned the real time of the Internet search, the story changed again. Brent Dennis then remembered that maybe he had been on the family computer after all. His attorney has said Dennis will be cleared once the full story can be told.

A preliminary hearing in the murder case is scheduled for August.

Footnote: “Sweet” formula anti-freeze was outlawed by 17 states, but not at the federal level. The formula for most commercial brands was changed in 2013 after the industry reached an agreement with consumer safety organizations.