- I'm craig melvin,
And this is "dateline: Secrets uncovered."
She was a wife. She was a mother.
- She was the most amazing woman I've ever met in my life.
- And then, suddenly, one day, she was gone.
Poisoned by carbon monoxide.
- He's like, "I couldn't get a pulse,
I couldn't get a pulse."
- Her husband blamed a faulty water heater.
Police blamed him.
- You don't think this is an accident.
- No. - There was just one problem,
And it was a big one.
No one could figure out exactly how he might've done it.
- He's an expert in gases. He's an anesthesiologist.
- Murder or accident?
- Did you kill your wife, kathy?
♪♪
- Hello, and welcome to "dateline: Secrets uncovered."
Kathy and mark wangler built a comfortable life
Over their 29-year marriage. That's until a silent killer
Crept into their home: Carbon monoxide.
Kathy died from what looked to be
An accidental poisoning,
Then a secret diary surfaced,
Leading investigators to wonder
Was this actually a carefully crafted murder?
Here's kate snow with "deadly exposure."
♪♪
- He's come back to where it all began,
To the town, the streets he knew so well,
Remembering the old times when life was simple,
Love was young, and the future held so much promise.
Taking time to reflect on how it happened.
A few days from now, it will all be over,
One way or another.
- Our story begins in lima, ohio,
On a frantic, pre-dawn morning, September 4th, 2006.
Dr. Mark wangler says he woke suddenly
In the downstairs master bedroom
To the sound of an alarm.
What kind of an alarm? - Just, uh, a loud,
Piercing noise,
And was able to determine it was the carbon monoxide detector.
Uh, then I ran to check on kathy.
- Kathy wangler was 48 years old,
And for most of her life, had suffered from epilepsy.
She was sleeping upstairs. - I went in, and, uh,
Shook her, and called out to her, and screamed at her.
But, uh, she wasn't responsive.
I called 911. - And you tell them
That she's having a seizure.
- Yeah.
- You remember doing cpr? - Yes, I do remember
Doing a cpr.
- Next door neighbor diane stuber
Saw the rescue squad at the wanglers' home.
- So I went over and I said to mark,
"mark! Did she-- did kathy have a seizure?
"and he's like, 'I couldn't get a pulse,
"'I couldn't get a pulse, I couldn't get a pulse'."
[sirens]
- The emts took kathy to lima memorial hospital.
Mark followed along and diane stuber was close behind.
The news came in a matter of minutes.
Kathy was dead
Of acute carbon monoxide poisoning.
Do you remember when they told you
That she had passed?
- No, I do not. - Why do you think
You don't remember any of that?
- Well, I was poisoned with carbon monoxide.
- It's an odorless, tasteless, colorless gas,
But as a doctor, mark wangler says
He knew had been poisoned with carbon monoxide,
Because his head hurt and he felt so disoriented.
Neighbor diane stuber says she remembers
How mark took the news of kathy's death.
- He sobbed like a baby. The tears were rolling
Down his cheeks, and he was just, like,
You know, this. He couldn't believe
That it had happened. - I wanted to see
Kathy's face. I wanted to see kathy.
- To say goodbye?
- Yeah, it was tough.
- Kathy's family members drove to lima memorial.
They'd only been told there'd been some
Kind of accident. They found their way
To a waiting room. - They told us in the room,
And then that was a very hard moment.
It's hard to see your parents cry.
And then, turn around, call your brothers and sisters.
♪♪
- Mark wangler called his two sons,
Nathan and aaron,
Who were living in cincinnati.
Aaron was in his second year of college.
- I just remember it just screaming and crying.
It was horrible.
- The brothers rushed home to their father in lima.
- I remember him and my brother and I
Just holding each other, and all of us just sobbing
And crying, and, like, his body was, like, shaking
From crying so hard, like...
- Thousands of people are accidentally poisoned
With carbon monoxide every year.
It usually happens when something
Like a space heater or a furnace
Or a water heater malfunctions.
Investigators wanted to find out quickly
What went wrong at the wangler home,
So a detective came to speak with mark wangler
Here at the hospital.
Former allen county sheriff sam crish
Ran the detective bureau back then.
He says dr. Wangler mentioned the water heater.
- Dr. Wangler made a comment
That they were having problems with this water heater
In the past few weeks.
The flame would go out occasionally.
Uh, it felt that that was the problem
Due to the carbon monoxide detectors going off.
- Diane stuber remembers her husband worried
About the wanglers' water heater, too,
Saying the exhaust pipe on the roof
Wasn't placed there correctly.
Could that have caused a backup of carbon monoxide
Into the house? - And he told mark,
I said, "that would scare me to death, mark."
- It sounded like mark wangler was lucky to be alive.
Kathy just happened to be the one
Sleeping upstairs that night. Mark was downstairs.
It seemed like a sad but explainable accident.
But as it turns out, it wasn't so simple.
- Growing suspicions that something was missing.
- We walked around the house, we looked at the water heater,
We looked at the other appliances.
We just couldn't find a source. - For the carbon monoxide.
- Right, because the appliances appeared to be working properly.
- When "dateline: Secrets uncovered" continues.
♪♪
- 48-year-old kathy wangler had a personality
That filled the room.
Now she was gone, killed by carbon monoxide.
For her family and friends, it was a terrible loss.
For her sons, nathan and aaron, it was devastating.
As aaron told us, they adored their mother.
- She was amazing.
The most amazing woman I've ever met in my life.
Did everything for everyone. Always put herself last.
Always put my brother and I number one priority in her life,
And my dad. - And she certainly
Didn't want to be defined by her epilepsy.
It started when she was a little girl,
But medication seemed to keep it under control for the most part.
Kathy was 15 when she met mark wangler.
- Grew up in a little town of, uh, fort recovery, ohio,
And, uh, it's about the middle of the state,
Down near the ohio/ indiana border.
Small town of about 1200 people.
- What was that like?
- I enjoyed it. I really loved
Growing up in a small town.
We played softball in the backyard,
And, uh, you know, knew all your neighbors,
You knew everybody in town, and everybody in town knew you.
My dad owned a hardware store. - That's where mark met
Kathy's grandfather, a customer at the store.
One day, when mark stopped by the grandfather's house
For a visit, he met kathy.
Kathy's mother remembers a couple of months later,
Mark was back. - The kids come in, they go,
"mark's here!" I go, "mark who?"
And they said, "mark, uh, wagular guy."
And I said, "where's he at?"
And he was out, he brought his guitar,
And he came and sat on the backseat--
Back of the tru-- uh, uh, his vehicle,
And he was t-- strumming a car-- guitar,
Singing to kathy. - Serenading her?
- Yes. Yeah.
♪♪
- They started dating, and a few years later,
In 1977, mark and kathy got married.
He was 21, she was 18.
They held their wedding in a catholic church,
But by then, mark had embraced an evangelical christian faith.
- They were as happy as two people I'd ever seen.
- And it turns out,
The quiet young man from fort recovery
Had big ambitions. He wanted to be a doctor.
Kathy worked to put mark through med school.
Things were tight. Were you happy?
- Yes. - In those years.
- Yes, I was. It was a great marriage.
- You had two boys. - Correct.
- Nathan and aaron were born right as mark
Was beginning his practice. - We're the family
You would give hugs and kisses every morning
And every night before you go to bed,
And when you leave for school
Or even if you were just going out to, you row,
Hang out with your friends, wherever, like,
We always kiss and love, we're always, like,
A very close family. - They moved to lima
In 1990, and by then, the christian faith
Had become very important to mark wangler.
They joined grace baptist church.
What was it about this particular church
That you and kathy both thought was f-- a right fit?
- Two things, um,
One of 'em is we felt that the-
The people there were friendly,
And, uh, the pastor was correctly preaching god's word,
And, uh, the second thing is is that they had
A very active, um, children's program
Or youth program.
- Mark and kathy and the boys.
- At the time, mark's medical practice
Was growing.
[all] - merry christmas.
- After those early years of doing without,
The family was now well-off.
They took the boys on vacations, camping, europe.
Kathy went back to school,
Did some substitute teaching.
Life seemed to be going well for the wanglers.
Next door neighbor diane stuber
Was fond of both kathy and mark.
- Mark was more reserved. Um...
Nice man, very patient and caring person,
Um, would help you out, do anything for you,
And, you know, he had his little peculiar ways about him.
Was a little dorky.
And he looked different from other people.
Until you get to know mark
And he is the most wonderful person
That you could ever meet.
Kathy was a lot of fun to be around.
She was bubbly, she had a crazy laugh,
Um, loved life, um,
Just a lot of fun.
[laughing]
- But now after 29 years of marriage,
Two boys, a prosperous life,
Kathy wangler's life had ended
In one terrible morning.
How did it happen?
Mark wangler had told investigators
He thought it was probably the water heater.
So, they checked that out
And the allen county prosecutor was concerned
By what they didn't discover.
Prosecutor jurgen waldick often examines
The scenes of unexplained deaths in allen county.
- We walked around the house. We looked at the water heater.
We looked at the other appliances, the gas furnace,
The gas logs, uh, the garage,
And also the bedroom where, uh, kathy wangler died.
- They couldn't find a problem with any of the appliances.
- We just couldn't find a source.
- For the carbon monoxide?
- Right, um, because the appliances,
Uh, at that point had appeared to be working properly.
- Investigators now had a mystery on their hands.
They returned to the wangler house
To do some rechecking.
And then in December, 2006,
Three months after kathy's death,
Mark wangler says investigators told him
They had looked at everything.
They still hadn't known what happened, he said,
But they were satisfied it was an accident.
They were settled?
- That's what I was told.
- Mark was slowly trying to build a new life
But some members of kathy's family
Weren't ready to move on.
They were still asking questions
And they thought the answers just might lie
With mark wangler.
- And I said we have so many questions
And nothing is being answered.
- What did kathy's family know that made them so suspicious?
- She got in the car.
The boys got in the car.
Mark was hanging on the side of the car
And kathy was driving away yelling at him.
- What kathy had told me was basically
Mark had an-an affair.
- That can't have been easy for your sister.
- She could never ever forgive him for that.
- When "dateline: Secrets uncovered" continues.
- Kathy wangler's death certificate said
The cause was carbon monoxide poisoning,
But what was the source?
By December 2006, three months after kathy's death,
That question had grown more urgent
In the minds of her family members
And sister diane wanted answers.
- It was kind of like the white elephant in the room.
None of us really wanted to talk about it.
And it, you know, the police weren't calling us.
We-- I felt as if nothing was getting done.
- So diane decided she had enough.
- So, I actually called mom
And she actually called the sheriff's department.
- And I said we have so many questions
And nothing is being answered.
- But it wasn't just questions kathy's family had.
They also had suspicions about mark
Because they knew something.
The wangler marriage was a disaster
And they wanted police to know the problems went back years.
- What kathy had told me was basically mike--
Mark had an-an affair.
- That can't have been easy for your sister.
- She could never ever forgive him for that.
- They manage to carry on but over the years
Kathy's family remembers simmering tensions
That could erupt into open warfare.
They say mark thought kathy gained too much weight.
She wouldn't clean the house.
She spent huge amounts of money.
Kathy got mad at mark a lot.
Diane recalls what happened right after
They took this family portrait.
Mark and kathy were fighting again.
- She got in the car. The boys got in the car.
Mark was hanging on the side of the car
And kathy was driving away yelling at him.
At one point, one of the boys jumped out.
There was a lot of yelling and carrying on
And then kathy left with the boys.
- Mark wangler admits things did go downhill
After the boys left for college.
He says kathy would get deeply depressed.
- With the boys being gone, she kinda lost her purpose
In life I would say.
- Were you working on it?
Were you trying to-- - yeah, we were in counseling.
- And then she was gone.
Kathy's family knew she had been sleeping upstairs
While he was downstairs, but then they heard
What mark had told investigators
And the collective alarm went off.
Mark said he was sleeping
With a towel under the bedroom door,
A fan blowing and the bathroom window opened.
That was because the toilet
In the master bathroom had overflowed
And mark said he wanted to keep the smell
Out of the rest of the house.
Kathy's family knew about the problem with the toilet
But they figured there was a different explanation
For the towel and the fan and the open window.
They believed mark knew
There was carbon monoxide in the house
Because he had somehow put it there
And he was protecting himself from poisoning.
How did you respond to that suspicion
That was placed on you?
- I was devastated.
- Five months after kathy died, her case file
Landed on the desk of a veteran detective
Clyde breitigan, since retired.
What's your instinct? - In reading reports,
I-I-I was sure that the water heater, the furnace,
And vent-free gas fireplace were not the source
Of the carbon monoxide.
So then you have to think, "okay, what else in that house
Could produce carbon monoxide?"
There was a generator in the garage.
There were two cars in the garage.
There was a snow blower in the garage.
Those all produce carbon monoxide.
- But of course, all those things
Need someone to turn them on.
You don't think this is an accident?
- No.
- Still if it wasn't an accident,
How could someone pull that off,
Fill an upstairs bedroom with enough carbon monoxide to kill?
Detective breitigan knew it sounded improbable,
But he kept thinking about the logic
Of that other detective, sherlock holmes.
- It was a matter of just eliminating
The impossible things and, at the end,
You're stuck with the improbable.
- And there's another clue breitigan
And the allen county prosecutor couldn't ignore.
Dr. Mark wangler had a specialty.
- I mean, he's an expert in gasses.
He's an anesthesiologist.
- That's right, an anesthesiologist.
A doctor who knows exactly how to put people to sleep.
Did he use his expertise to kill his wife?
In April of 2007,
Seven months after kathy's death,
Detective breitigan got a search warrant
For the wangler home.
He had a video tape running as officers seized a computer,
Papers, and mark's journals.
Detective breitigan says the journals
Really caught his attention.
- You'd have to read the whole thing,
And I-I cannot explain now. I wish I could.
It's just the-- he was at, like,
The end of his rope and I-I think he felt trapped.
- But now, all these months later,
Mark wangler's life was on the upswing.
He had reconnected with an old friend
Who shared his faith, esther vandigm.
A romance blossomed.
You ended up getting married, I think,
About a year after kathy's death.
- 14 months, correct.
- Some people might think that
That's pretty fast to bounce back.
- Yeah, we've heard that.
- And the wedding bells had barely stopped ringing
When detective breitigan got a second search warrant
Because by now he had come to believe
That mark wangler was a killer.
Breitigan thought that wangler had used an engine of some sort,
A portable generator of maybe the vehicles
To put carbon monoxide into the heating system
Of his home to kill his wife.
The detective wanted someone to take a closer look
Inside the heating ducts of the wangler home.
- And we went in and dismantled the ductwork
And took carpet samples and the registers out of the house.
- Investigators found a lab that would try to determine
If soot from an internal combustion engine
Could be found inside the heating ducts.
It would be months before they got results.
- Did you have any idea that as you were having
This busy, happy time investigators were still trying
To put a case together?
- We really didn't hear anything for a long time, hadn't we?
- Yeah-yeah, we didn't hear anything at all
For a long time.
- So, you-you plan a trip to zambia.
Why did you end up there?
- Uh, one of the churches in town--
A good friend of mine had gone to zambia
With several people from his church.
- They learned that people in zambia
Were in dire need of fresh water,
So mark and esther joined a church mission
To help dig wells there.
After three weeks, it was time to go home.
You land in atlanta. - Yeah.
- And your son calls.
- He said, "do you know some guy named breitigan?
They were banging on the door."
- That's the detective. - Yeah.
- So you knew then.
- So, we knew then, um, in the atlanta airport
That there must have been an indictment
And they were at the door to arrest mark.
- The lab results were in on that ductwork.
- The prosecution's case motive.
- We have some diaries that are pretty dark
And kind of lay out what the state
Of the marriage was.
- "thoughts of suicide are a little strong again.
"satan is attacking in a new way this time."
- If your marriage is so bad that you want to kill yourself,
Uh, what other things are you willing to do?
- And means.
- You tell the jury what, if anything, you noticed
In that particular bedroom?
- I observed soot-like markings on the wall
Directly above the register-- the heat register in there.
- When "dateline: Secrets uncovered" continues.
♪♪
Welcome back to "dateline: Secrets uncovered."
I'm craig melvin.
14 months after kathy wangler died
From carbon monoxide poisoning, her husband mark remarried.
Investigators suspected that mark murdered kathy
And now believed they had collected
Enough evidence to prove it.
Soon, the life that mark was building
With his new wife esther, would be turned upside down.
Here's kate snow with "deadly exposure."
- On September 19, 2009, as mark wangler
Boarded a plane from atlanta to ohio
He knew he was about to be charged with
Killing his first wife three years earlier.
- I felt that I needed to come back and, uh,
And-and clear my name.
- Two days later, sheriff's deputies
Came to the couple's home and arrested mark wangler.
He was charged with aggravated murder.
The trial took place in March, 2011
At the allen county courthouse.
Prosecutor jurgen waldick didn't have fingerprints, dna,
Or an eyewitness but he believed
The evidence would show that dr. Mark wangler
Killed his wife while she was sleeping
Using engine exhaust containing deadly carbon monoxide.
- I have someone who's died of carbon monoxide poisoning.
Uh, a really high level-- 69%.
I have a defendant who has really low levels.
We have no legitimate source of carbon monoxide
In the home, and we have some diaries
That are pretty dark and kind of lay out
What the state of the marriage was.
- And that's where prosecutors started--
With the marriage, the motive.
Kathy's family bolstered the argument
That the marriage was a miserable one.
- He criticized her weight. He didn't like her hair.
- Did you ever hear mark criticize kathy
On the topic of money?
- Yes, he didn't like her shopping.
- Prosecutors suggested mark had become
Increasingly angry about his wife's spending.
Just after kathy died, mark showed investigators
This cash, jewelry, and credit cards
He found in kathy's car.
So, why not divorce? Friends and family
Testified kathy wouldn't leave the marriage
Because she was afraid mark would cut off her money.
As for mark-- - the defendant
Was deeply obsessed with religion,
And a divorce would cause him to lose
His standing and reputation in the church.
- And if mark and kathy were stuck
With each other and fighting all the time,
His journals painted an even bleaker picture.
The man who wrote them wasn't just unhappy,
He was depressed, and according to prosecutors,
Desperate enough to kill.
Detective breitigan took the jury through
Each painful entry. - "I am tired of her lies
"and hiding huge amounts of money from me.
"she turns away each time I kiss her.
"she continues to reject my love towards her.
"I truly long to serve jesus, but I became weak
"from the wounds satan throws at me
From within my own family." - just two months
Before kathy wangler died, mark wrote this.
- "thoughts of suicide are a little strong again.
"satan is attacking in new way this time.
Using car exhaust." - that's a real red flag--
Tells you the state of someone's marriage.
At least in-in our assessment, that, uh, if your marriage
Was so bad that you're willing to kill yourself,
Uh, what other things are you willing to do?
- And that mention of car exhaust
Really got their attention.
One depressing entry after another,
Mounting evidence of a man in misery.
In the eyes of prosecutors, a motive.
And that 911 call raised even more suspicion
As far as the prosecution was concerned.
- It just didn't sound like he was doing cpr on the 911 call.
It sounded like the whole thing was staged.
- And if dr. Mark wangler was doing cpr,
Why would the fire chief find kathy
On an air mattress? - For adequate compressions,
It should be on a hard surface, yes.
- Okay, is that pretty basic cpr stuff?
- Yes, that's basic cpr.
- But something even more important crossed
The chief's mind after he found kathy,
And this was a huge red flag for prosecutors.
He said kathy's body was cold to the touch.
Odd, since mark told 911
Her heart stopped beating only minutes before.
- We discussed with each other in the ambulance
On the way to the hospital that she was-she was cold.
- Which would've been unusual for someone
Who had, just minutes before, quit breathing
And the heartbeat. - That's correct.
- The er doctor backed him up on that.
- She had a rectal temperature that was quite low.
Um, my documentation said it was, like, 94.
- The doctor also testified the body
Seemed to be getting stiff.
- It seemed like she'd been, um, dead for a while.
- In other words, dead before her husband called 911.
There was more. The prosecution suggested
Mark wangler's grief was phony.
- What was his emotional state that you observed at that point?
- He was acting like he was crying, but I didn't really see
Normal stuff when you cry, you know?
- In the days that followed kathy's death,
Investigators tested and retested
The water heater and other appliances.
Prosecutors reminded the jury there was no sign
Any appliance had accidentally released carbon monoxide,
And that was the crux of the case.
- It either had to be the water heater
Or-or it was murder. That's the bottom line.
- And, if it was murder, how would he have done it?
Prosecutors believed mark wangler closed
All the heating vents except the ones in kathy's room.
Then, he must have shut the doors to the furnace room,
Except for the one leading to the garage.
He could've started a car or a generator, or maybe both,
And filled the garage with carbon monoxide.
The carbon monoxide would then find the only open path--
Down the stairs into the furnace.
The deadly gas would then travel through
The heating ducts and out the vents
In kathy's room. They pointed to pictures
Taken of kathy's room after she died.
- Can you tell the jury what, if anything,
You noticed in that particular bedroom?
- I observed, um, a soot-like marking on the wall
Directly above the register-- the heat register in there.
- Nobody actually tested that stain on the wall
Before it was painted over, but prosecutors were prepared
To show that engine exhaust had come through
The heating ducts and out those vents.
Prosecutors now presented the key scientific evidence
Designed to wipe out any remaining doubt
About the source of the carbon monoxide.
Lab chemists had tested the inside of the heating ducts,
And said that they indeed found soot
That shouldn't have been there.
- Can you say, to a reasonable degree of scientific certainty,
That the exhaust from a combustion source
Was directly introduced into the ventilation system?
- Yes. - And can you say,
To a reasonable degree of scientific certainty,
That the water heater was not the source of the soot
In the ventilation system? - Yes.
- Devastating for mark wangler's case?
Maybe, maybe not.
- Is the prosecution's case all just hot air?
The defense is about to take the floor
And put their witnesses on the stand.
Coming up.
- Ladies and gentlemen, you will hear
From our experts that this is junk science
As applied to the facts of this case.
You will find that there is reasonable doubt
That you may even find that the water heater did this,
But regardless, you will not find that dr. Wangler
Murdered his wife, 'cause he did not.
- When "dateline: Secrets uncovered" continues.
- Dr. Wangler, did you kill your wife, kathy?
- Absolutely not. - He had waited
More than three years to defend himself.
All that time, his sons stood by him
And against their mother's family.
- When you have your family stabbing you in the back
And trying to destroy your own family
Or what you have left, it's-it's hard. It hurts.
- It was time now for the defense to present its case.
Time for defense attorney, chris mcdowell,
To show the jury a different version
Of the man who stood accused.
In his opening argument, mcdowell said
Mark was, above all, a devoted christian
Who would never commit murder.
- Mark did not believe that it was good enough
Just to profess the words of christ
Or to go to church, he felt that he had to live it.
- Mark wangler's defense came down to this--
His wife died in a horrible accident.
The prosecution never proved a crime was even committed.
- Ladies and gentlemen of the jury,
Dr. Mark wangler is innocent.
This case has been brought as a result
Of a poor police investigation. An investigation,
Despite what you just heard from the prosecution,
Did not eliminate fugitive carbon monoxide as a source
From the hot water heater. - The water heater
Was now at the heart of the wangler defense.
If the jury believed it malfunctioned
That night and could've sent carbon monoxide
Into kathy's room, that was reasonable doubt.
- Are you worried that a jury won't, in the end,
Believe your story? - Sure.
It's always a possibility.
- Do you think about what it would be like?
You faced up to the rest of your life in prison.
- I try not to for the most part.
- Sons aaron and nathan provided key testimony.
- How would you describe your father?
- He's a great man. Very humble, passionate,
Uh, caring. - Very relaxed,
Down to earth, um, very humble.
- Have you ever, for a moment,
Doubted your dad's innocence? - Never once.
- Both aaron and nathan said they believed
Their parents really did love each other.
- Up to the day of her death, uh, do you believe
That your father loved your mother?
- Absolutely. - And then, the defense
Turned to the mark wangler journals,
With their depressing entries about the marriage.
The defense challenged the detective.
Didn't the diaries portray a man working on his marriage?
- Mark, uh, prays for a good relationship
With his wife, correct? - Yes, he does.
- And he prays that his wife will also sort of see the way
And work on the relationship too, doesn't he?
- Yes. - Then, the forensic evidence.
Prosecutors had said kathy's low body temperature
Showed mark had killed her with carbon monoxide
Before he called 911, but the question was
When exactly did that poisonous gas kill her?
The prosecution argued she was already dead
When her husband called 911 because her body
Was so cold, but how cold was it?
Apparently, the er doctor got the temperature wrong.
- This is the nurse's handwritten notes,
Indicating that the body temperature--
The rectal temperature was actually 1.5 degrees more
Than what you had written in your other notes.
Is that correct? - Mm-hmm.
- Is that yes, ma'am? - Yes.
Yes, I'm sorry. Yes. - Okay.
- So, kathy's body wasn't as cold as the doctor thought.
Considering this, a leading forensic pathologist
Testified her heart could easily have stopped
Exactly when mark wangler said it stopped--
During the 911 call.
The defense also had to knock down evidence
From the wisconsin lab. You remember,
The lab experts said they had found soot
Inside the wangler's heating ducts
That came from engine exhaust.
- This is junk science as applied
To the facts of this case.
- Mcdowell said other bigger reputable agencies
Like the fbi and the ohio state criminal lab
Refused to do the testing.
It was too unreliable.
- These people in wisconsin said,
"we've never done it before,
"but we can try it."
- Mcdowell attacked the lab's data,
Its record keeping and its expertise.
- Prior to your work and involvement in this case,
Uh, you had no previous experience
In conducting analysis on duct work, did you?
- No, we've not done duct work before.
- And then, this question,
Did the lab consider other sources of soot?
- You would agree that candles are
A potential source of soot, correct?
- Yes, that is correct.
- Candles, the wangler house was full of them,
According to testimony from several witnesses
Like son aaron wangler.
Maybe that's why the heating ducts
Were full of soot.
- Do you recall if, uh, your mother ever burned
Any candles in the home, aaron?
- All the time.
We had tons of candles.
- And remember those soot stains
Coming out of the registers in the room where kathy died?
That was aaron's old room.
- Those marks were actually there
Before I moved for college,
So that is back in '04.
- The defense said the prosecution's murder scenario
Involving vehicle exhaust and the furnace
Was preposterous.
It had to be the simple explanation.
Kathy's death was an accident.
And now came the most important testimony
In the defense's case,
An environmental toxicologist testified
The most likely source of carbon monoxide
Was the water heater.
- What was the closest source of, uh, carbon monoxide?
- The gas fire water heater in the basement of their home.
I think, as I recall, pretty directly
Below her bedroom two floors up.
- The water heater, he said,
Was a disaster waiting to happen,
One code violation after another.
- My major concern was that
This water heater wasn't in the open
As most water heaters are.
It was in a sealed cabinet.
- Closed up in that box, he said the unit
Could have been deprived of oxygen,
Creating a risk of carbon monoxide.
He said venting was another problem.
The vent cap was the wrong kind,
And the exhaust pipe was set too low on the roof.
It was all installed so poorly, he suggested,
That deadly carbon monoxide could've backed up
Into the home.
The water heater was so faulty, said mcdowell...
- You will find that there is reasonable doubt.
That you may even find that the water heater did this.
But regardless, you will not find
That dr. Wangler murdered his wife,
Because he did not.
- Coming up...
- You had expert testimony on both sides of this.
- Right.
- Did it come down to science for you?
- I don't think so. - No.
- The verdict.
- We the jury being duly impaneled and sworn
Find the defendant, mark a. Wangler...
- When "dateline: Secrets uncovered" continues.
- Welcome back.
Kathy wangler's death divided her family.
One side was convinced that her husband, mark,
Secretly plotted to kill kathy in order to free himself
From a suffocating marriage.
The other side believed her death
Was a tragic accident.
A jury would decide mark's fate.
But first, he spoke with us.
Here's kate snow with the conclusion
Of "deadly exposure".
- On a cold Sunday in early March 2011,
Dr. Mark wangler, who was standing trial for murder
Seemed to want a moment with those who were standing by him.
During a weekend break from the trial,
He showed us around his hometown,
About an hour's drive from lima, ohio.
His old house is still there.
His sister and brother-in-law
Own the family hardware store now.
[laughter]
It was a strange homecoming.
With so much at stake, he seemed so relaxed.
- Yeah, I haven't worked in here since 1977
And there's some of my [indistinct].
Okay, enough reminiscing.
- Mark wrangler wanted to see his mother,
A chat and then goodbye.
Was it just for now? Or for good?
- Now this is the last one.
I hope I get to come back next week.
- I hope so. - I'm pretty confident.
- No, I am too.
- I'm feeling pretty good about it.
- Even on this night before closing arguments,
Esther and mark held to their routine,
Like choir practice at grace baptist.
Mark wangler never testified on his own behalf.
Would it matter?
He was as quiet as ever, and so hard to read.
But not esther. She was a wreck,
Wondering what will happen? What are the jurors thinking?
In a courtroom back in lima, closing arguments,
Where defense attorney chris mcdowell insisted
The prosecution failed to make its case.
- Did you hear them explain to you
How dr. Wagner allegedly committed this crime?
No, you didn't hear any of it--
Really hear any solid theory on that.
- It was an accident, he said.
It was the water heater.
- The government has failed to disprove it as the source.
As a result, there's reasonable doubt.
You must turn a verdict of not-guilty in this case.
- In his closing argument, prosecutor jurgen waldick
Outlined his murder scenario for the jury,
The heating vents, the doors, all shut
To create a direct pathway from the garage
To the furnace to kathy's room.
- Then, he started the car,
Or the generator, or maybe both.
And then he waited.
- And the water heater?
It was checked over and over, he said.
Sure, there were code violations...
- But you know what? That didn't kill her.
- And then, the jury got the case.
Two weeks of testimony, much of it dense and scientific,
What mattered most to the jury?
- You had expert testimony on both sides of this.
- Right.
- Did it come down to science for you?
- I don't think so. - No.
- An afternoon passed, and by the next afternoon,
Their verdict was in.
Esther was sitting with her son and mark's family.
Kathy's family was seated on the other side.
- We the jury being duly impaneled and sworn
Find the defendant mark a. Wangler
Guilty of aggravated murder. - Yes!
[sniffling, crying]
- Dr. Mark wangler was sentenced to life in prison,
Eligible for parole after serving 25 years.
- Mr. Wangler, you violated the ten commandments.
Thou shall not kill.
You also violated the hippocratic oath.
As a doctor, you shall do no harm.
- Do you remember that moment?
- Yeah, um, I was shocked, but just beyond sad.
I just bawled. I cried hysterically.
And, I mean, thinking about it still,
Like, makes me wanna cry, because it's hard, you know?
And like, I only have one parent now
And they took him from me, so...
It's hard.
- We spoke with jury members, both on camera and off.
They said it was the simpler things
That convinced them, the 9-1-1 call,
The diary, the body temperature.
And the malfunctioning water heater?
They didn't buy it.
- Walden and a couple of the other jurors
Were very knowledgeable on furnaces and hot water heaters,
So they gave their opinion of how they felt
That it could've happened or could not have happened.
- You ruled out the water heater.
- Pretty fast. I think within the...
What? First hour or two?
- To this day, do you have any idea
How this crime might have been committed?
- I don't. - No.
- No, ma'am.
- It was vindication for kathy's family,
Especially her mother, who addressed the court.
- We know you have always been a very selfish person,
Who really did not care about our beautiful daughter,
Only yourself.
Nathan and aaron, you are our first two grandchildren.
Our family love you. We always will love you.
And I hope someday we can have a connection
Like we had before.
- After his sentencing, mark's wife esther
Visited her husband in prison as much as possible.
- I just hope and pray that...
He doesn't get hurt.
Or worse.
- Detective breitigan says
There were no winners in this case.
He was only following evidence, he says,
That led to a very sad conclusion about mark wangler.
- I think there was a lot of rage in him,
And although he wanted to live right,
Or he wanted to have a good marriage,
I-I think he couldn't, so...
- You think he didn't see a way out.
- I don't think he saw a way out.
- That's all for this edition of "dateline: Secrets uncovered".
I'm craig melvin. Thank you for watching.