Kathy Wangler's Carbon Monoxide poisoning death explored

A Lima, Ohio, mother-of-two, Kathy Wangler, died of carbon monoxide poisoning during the early hours of September 4, 2006, Labor Day weekend.

Her husband, a renowned anesthesiologist, Dr. Mark Wangler, made a 911 call while also administering CPR. Paramedics arrived at the location, but to no avail as she died within the hour.

Kathy's death initially seemed like an unfortunate accident, but the investigation that followed revealed numerous secrets and lies that the couple's marriage was built upon. However, the case took a shocking turn when her husband became a person of interest and was convicted of the alleged murder. People came forward with contrasting opinions on the case, but the jury had declared its verdict.

Dr. Wangler is currently serving a 25-year long jail term in Ohio and Dateline: Secrets Uncovered's upcoming episode will narrate the tragedy of Kathy Wangler's unfortunate death due to carbon monoxide poisoning on September 7, 2022, at 8 pm ET on Oxygen.

Read further to learn key details about the case ahead of the episode premiere.

Five key facts about Kathy Wangler's death by Carbon Monoxide poisoning

1) Kathy Wangler's death was allegedly caused by engine exhaust

Mark Wangler was charged with his wife's murder and convicted in the subsequent trial (Image via Oxygen)

During Dr. Mark Wangler's trial, the evidence introduced in court during the proceedings included images of soot marks right above the vent in her room from the crime scene. The prosecution claimed that the images were taken shortly after Kathy's death on September 4, 2006.

According to them, this was obvious proof that she was killed with engine exhaust intentionally directed to the room she was sleeping in via air ducts to cause carbon monoxide poisoning.

However, Dr. Wangler's defense attorney Chris McDowell reportedly claimed that he had witnesses to confirm that the stains were present much before the tragic accident. The former couple's son, Aaron Wangler, testified in court, saying:

"Those marks were actually there before I moved to college. So that was back in '04. I never really cleaned my room that much at all, to be honest."

The older son Nathan Wangler added:

"We enjoyed candles. We burned a lotta candles....throughout the entire house there's actually discoloration on the walls, on the ceiling."

The soot marks were never subjected to examination by detectives, given that Mark repainted the wall in the months after Kathy's death.

2) Dr. Mark Wangler's journals were used as key evidence

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Kathy Wangler's mother, Sara, tipped authorities on Mark's journal, which was later procured from the former couple's Lima, Ohio, home during the investigation. The entries were incriminating, comprising of his thoughts about Kathy and their marriage. The journal was written after his marriage counselor advised him to write down his emotions and be forthright about them.

3) Kathy Wangler died before her husband called 911

On the day of the incident, Dr. Mark Wangler called 911 and said that he tried to administer CPR to his wife, but Kathy remained unresponsive. However, during the trial, the prosecution alleged that his attempts to perform CPR on Kathy were a sham considering that she was almost certainly already dead by the time he called 911.

According to testimony from an emergency department specialist, Rena Stein, Kathy Wangler's body was already cold when paramedics found her. Stein said:

"What I can say is that it seemed to me, from my experience of 22 years, that she'd been dead for much longer."

4) Kathy and Mark Wangler were sleeping in different rooms on the night of the incident

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Initially, it was stated that Kathy Wangler and her husband Mark would sleep in separate rooms because of their different sleeping habits. Kathy was a night owl while Mark went to bed early.

Dr. Mark Wangler reportedly told CBS 48 Hours:

"I would go to bed earlier because I get up earlier to go to work and Kathy was a night owl."

The investigation revealed that the two would sleep separately because of the problems they were facing in their seemingly perfect marriage. On September 4, 2006, Kathy was sleeping on the second floor while Mark slept in a room on the first floor. Recalling the incident, Mark claimed that he woke up feeling "nauseated." He added:

"I remember vomiting somewhere along the line as I was going through the house. And I then go up to check on Kathy."

5) Kathy Wangler allegedly told friends that Mark was out to ruin her

Kathy Wangler was discovered by her husband Mark on the night of the carbon monoxide poisoning incident (Image via Oxygen)

Kathy and Mark Wangler were going through a rough patch in their marriage when the incident occurred. The differences between the couple kept growing to the point where they got into physical fights and started sleeping in separate rooms.

In the summer of 2006, as conflict increased, Kathy confided in a number of friends and shared her issues with them. Her friend Sherry Miller stated:

"She had told me that her husband was out to destroy her - financially, emotionally, psychologically, in the community, at her church. That he was in the process of working to destroy her."

Rodney Null, one of her Ohio State University professors, also commented on the situation, saying:

"And I say to her, 'Well, take care of yourself' - the usual getting-ready-to-say-bye kind of comment. And she says, 'Oh, I will you have to when somebody's trying to destroy you.' And she says, 'I mean that literally.'"

Null added:

"And three days later she's dead. I gotta tell you, that leaves a feeling in the pit of your stomach, your gut, that something sinister, something evil's happened."

Tune in to Dateline: Secrets Uncovered this Wednesday, September 7, to learn more about Kathy Wangler's alleged murder case.