Original subtitles

(gun shot)

When a murder is committed, it's always a race against time

to find the truth, to separate fact from fiction,

to catch the killer and to make sure that justice is served.

But what happens when the truth vanishes with the victim?

I'm Dr Richard Shepherd, and I've spent my entire career

as a forensic pathologist, performing nearly 23,000 autopsies,

including on some of the most high-profile cases of recent times.

I've learnt that the dead don't hide the truth and they never lie.

Through me you'll be hearing directly from the victim.

From a state-of-the-art laboratory with ground-breaking technology

that uses digitally scanned sampled bodies,

I'll be investigating a series of intriguing murders

where, from the victim's bodies,

I'll be revealing to you the truth behind those horrific crimes.

(camera clicks)

(bell tolls)

Centerville, a small, quiet town in rural Iowa,

the heart of the American Midwest.

Serious crime is almost unknown,

but in May 2018

a terrible house fire shocked this community.

Inside firefighters discovered the badly burnt body of a man.

It looked like a tragic accident,

but could it have been something much more sinister?

And could the body tell the story of what had happened?

(country music)

Centerville is a small, close-knit community

of about 5,000 people.

Everybody knows everybody.

We know their families, we know their history.

Everybody looks out for one another.

It's how it's always been.

Many of the families have been there for generations.

A community that has a strong agricultural tie,

so most of the families are farmers

who have been farmers for generations.

We have one middle school,

one high school for all the students.

They all go to the same school, participate in the same sports.

I was born and raised in Centerville,

moved away for a few years.

When we started having a family we decided to move back,

just because of the community and how close it was.

'But at 7.30am on Saturday May 5th 2018,

'Centerville's peaceful life was turned upside down.

'Barbara Pasa was driving to a soccer tournament

'where her children were due to play,

'but before she got there,

'she received several shocking phone calls from her neighbours.

'Her house was on fire.'

'Barbara rushed back, knowing her husband Tim was in the house.'

(Moore) One of the neighbours was driving, leaving his house,

saw fire coming from the Pasa residence.

Two neighbours from across the street went in the front door,

looked to the left and saw charring and smoke.

'They acted fast and called local firefighters on 911.

'They arrived within minutes.' (sirens wail)

(firefighter) "OK, 0-1-1-11."

"Let the fire department know that there is a lot of smoke

coming out of the east side of the house."

When the fire department first got there,

they saw black smoke rolling from the east side of the residence,

which is where the master bedroom is located.

They immediately started to extinguish the fire.

(indistinct chatter over radio)

'All four of the town's fire trucks arrived.'

(siren wails)

There was a lot of smoke.

One of the firefighters that went in to battle the blaze

did suffer from smoke inhalation and had to be taken to the hospital.

(officer) "Know if anybody's home?"

'Neighbours told police officers on the scene

'they thought there were people inside.

'They called in Assistant Chief of Police Mike Moore.'

I knew the occupants of the residence,

so I was just unsure what we were going to find.

I was initially informed that there may be three bodies inside.

I was fearful at that time that it may be the children involved.

'When the firefighters finally managed

'to get into the master bedroom, they discovered a terrible sight.

'Barbara's husband, Timothy Pasa, was found dead on the bed,

'and his body had been severely damaged by the fire.'

The most obvious injuries

were the terrible burns present on Tim Pasa's body.

Doctors use the "rules of nines"

to estimate the surface area of the body that's been damaged.

I can demonstrate that on this sample body

on the digital autopsy table.

The head counts for nine percent,

the arms are nine percent, the upper chest is nine,

the abdomen is nine, the legs are nine, front and back,

and the back of the body is split into nines as well.

And using that estimation,

we could work out that 97 percent of the surface of Tim Pasa's body

was damaged by fire.

It's most unusual to find

such a high percentage of burns in a house fire,

and the burns on the body are estimated by doctors

as first, second or third degree.

First-degree burns are like sunburn, just reddening of the skin.

Second-degree burns have blistering,

if you touch something hot in the oven.

Third-degree burns are when the skin is damaged and burnt through,

exposing the muscle.

In Tim Pasa's case, most of the burns were first- or second-degree,

relatively superficial,

but the extent of the burns suggest that he wasn't moving,

that he was asleep at the time the fire was burning.

It was a tragic end to a family man.

(Moore) Tim Pasa was a well-liked guy.

Very well-known in the community,

whether it be through involvement

with his children's sports, school activities...

He was a member of a band for a long time.

Tim was born and raised here

and I believe he lived here all his life.

I have a lot of memories of Tim.

Our children were the same age

so they did a lot of activities together.

We'd sit together a lot of the times at sporting events.

'The most important thing in Tim's life was his family.'

Barb and Tim had been married for several years,

I believe it was 18.

They had two children that were both in high school.

She was also from the area and spent her entire life here.

I'd known Barb Pasa for probably 30 years,

was actually a friend of the family's,

grew up with one of my older sisters.

'They were a very normal family

'in a small town where things like this hardly ever happen.

'They simply weren't prepared for such a terrible tragedy,

'and neither was the rest of the community.

'Most of its emergency services are volunteers.'

Currently the Centerville Police Department has 11 full-time officers

and we have three reserved police officers.

Centerville Fire Department, it's a small department.

There's three full-time firefighters,

and the rest, it's a volunteer department.

'Now they had a fatal fire on their hands.

'They had to investigate how the fire started.'

We conducted a walkthrough of the residence shortly after the fire.

Started doing their investigation.

(indistinct radio chatter)

'As soon as Barbara arrived,

'she told the firefighters that Tim was inside.

'She feared the fire had been caused by a lit candle

'she had placed in the master bedroom.'

Barb told me that she had lit a candle

that morning before leaving,

because the dog had urinated in the bedroom

and she was using the candle to cover up the smell.

She advised that she'd set the candle on the nightstand.

When fire investigators found the candle,

it was on the floor next to the bed, on its side.

On the floor there was an unburned white spot

that was consistent with the candle being on the floor

at the time of the fire,

which means that the candle was sitting upright during the fire.

It did not fall from a nightstand or anything like that.

'And that wasn't the only thing

'that Mike and his fire department colleagues thought was odd.'

Tim's body was very badly damaged in the fire.

It was what I would call inconsistent

with the amount of fire damage

throughout the room where the fire took place.

The condition of Tim's body initially was suspicious,

but not enough to state that anything may be criminal.

'Mike decided that it was an unusual but still an accidental fire.

'All the emergency services left the scene.

'There was just one thing left to do, an autopsy on Tim's body.'

Any time there's a death investigation,

an autopsy will be completed.

'The autopsy was performed by the state medical examiner,

'pathologist Dr Dennis Klein.'

The cause of death and the manner of death

may not be immediately obvious

and the autopsy is the best way to get at these answers.

What was the injury, disease or poisoning

that ultimately led to that person's death?

Despite the burns,

most people die in fires by breathing in noxious gases.

And the most important of those is carbon monoxide,

which binds the haemoglobin in the red blood cells

and stops them carrying oxygen.

So that the blood, when it travels round,

can't carry the necessary oxygen to the heart or to the brain

and these organs eventually die

and the individual will then die too.

Carbon monoxide is present all round us, in our bodies.

If you smoke, you've got about 10% in your bloodstream anyway.

20% will give you headaches and you'll feel unwell,

but 30%, you're likely to die.

But what else can we find in the body when we look at it at autopsy?

When fires are burning, smoke is inhaled into the lungs.

And we can see that here.

The lungs themselves may be blackened,

but most importantly, throughout the trachea and the bronchi

there's little particles of black soot deposited

that shows someone was alive at the time the fire was burning.

But when Doctor Klein did all of these tests,

he had a big surprise.

Despite having burns on the outside of the body,

there were not the characteristic findings of soot

in the upper and lower airways,

which occur when a person breathes in smoke.

And then when we did a test,

looking at what's called the carboxyhaemoglobin saturation,

the amount of carbon monoxide that accumulates in the blood,

it was not elevated.

So these two very key findings were absent

and made me come to the conclusion

that Tim did not die of smoke inhalation

and that he was likely dead before the fire had occurred.

This is very surprising.

Generally a fatality at a fire scene has died as the result of a fire.

I've examined hundreds of fire deaths in my career,

and in my experience,

less than two in 100 were dead before the fire started.

Finding a victim who is dead

before the fire starts is always suspicious.

This autopsy had turned the investigation on its head.

I realised that this was going to be a difficult and complex case.

And we're conferring with law enforcement officers

who attend the autopsy.

I realised that I had more work to do,

but I realised they had a lot more work.

In May 2018,

a small town in Iowa was rocked by a fatal fire.

Tim Pasa, a well-known and much-loved family man, had died.

It was a tragedy for the whole community.

But at the autopsy, Tim's body revealed a horrific surprise.

Tim was dead before the fire started.

'The police needed extra help,

'so Iowa State Fire Marshal David Linkletter came to investigate.

'David teaches fire investigators to recognise the signs of arson,

'based on his own extensive experience.'

I've been a fire investigator since 2000.

And in that time I've been on well over 800 fire scenes.

I perform fire scene investigations

and hopefully try to determine how this fire originated,

how it spread through that area of origin,

and ultimately caused all the damage that it did.

'Two days after the fire took place,

'David and his team started to investigate

'the fire in the Pasa home.'

So we went down Monday, where they had prepared a search warrant

to re-enter the property, to take a look at the fire scene

and give an assessment of how this fire originated.

(siren wails)

'Something had troubled the local firefighters

'as soon as they arrived.'

(indistinct chatter)

'They couldn't hear any smoke detectors beeping.'

Neighbours, witnesses,

as well as the officers that responded and the fire department,

at no time did they ever hear any smoke alarms

going off in the residence.

Smoke detectors are pretty robust.

They can withstand a lot of damage and still keep working.

(beeping)

We discovered a smoke detector in the unburned portion of the house,

outside the kids' bedrooms, where it had been disabled.

There was a door that flipped open for the battery,

and that door was open and the battery was exposed,

rendering the smoke detector inoperable.

When we closed the battery door,

it worked like it was supposed to do.

Once we'd worked our way through the house,

we discovered a nine-volt battery on the floor,

near the door to the bedroom.

Near that area was also a melted smoke detector.

And directly above that was the line of demarcation

where a smoke detector once was,

and it had melted and fallen onto the floor.

And we very quickly were speculating

that that battery had been removed from the smoke detector

and thrown onto the floor before the fire event.

Obviously the battery just didn't fall out of that smoke detector.

'Both smoke detectors in the house had been tampered with.

'And that wasn't the only thing that troubled the investigators.'

'They'd been wondering about Barbara Pasa's behaviour.'

When she arrived on scene, she asked if she could see Tim.

I advised Barb that Tim was in the ambulance

but that he was in very bad shape due to the fire.

I allowed her at that point to go into the ambulance

and have a moment with Tim.

It wasn't until a couple of minutes later,

when I re-entered the ambulance,

and she advised me that she did not want an autopsy completed.

Yeah, and that to us was a pretty serious red flag,

and so it really provoked a lot of questions.

Why does she not want to have an autopsy performed

on her late husband?

'Barbara later said that the only reason she was opposed to an autopsy

'was she didn't want Tim's body any more cut up.'

Law states that the medical examiner has authority of that body,

and so even if a family member is opposed to that autopsy,

if a medical examiner feels that it's necessary,

an autopsy will be done.

Both the state police detective and a local police detective

actually wanted to attend the autopsy.

That's not a usual situation for a house fire.

So we knew that there was some concern.

Dr Klein was sure that Tim hadn't died as a result of the fire,

but could he have died as a result of natural causes

before the fire started?

If I was investigating this, I'd want to see the medical records,

and we know from those records that he had mild hypertension

and that his heart was slightly enlarged.

Firstly he'd have looked at the heart muscle to see

whether there was any evidence of thickening of the muscle.

The heart has two main pumping chambers, the left ventricle,

which pumps blood round the whole of the body,

which is the main, powerful pumping chamber, here.

He noticed that the heart muscle was slightly thickened

but not significantly so.

So while the heart was slightly enlarged,

it wasn't significantly so.

The second feature Dr Klein looked at were the coronary arteries.

These are the blood vessels

that supply oxygen to the muscle of the heart.

He'd have looked at those to see

if there was any evidence of furring up,

a blockage of those arteries, and there wasn't any.

So Dr Klein was able to conclude that there was no evidence

of significant natural disease with the heart

that could have killed Tim Pasa before the fire started.

So Tim must have died from unnatural causes.

Dr Klein would have looked carefully at the chest.

He found no evidence of any bruising, any fractured ribs,

any bullet wounds or any stab wounds.

Is there any evidence of any injury to the face, the skull, the brain,

that might indicate blunt trauma?

Then he perhaps had a look at the neck

to see whether there was any evidence of strangulation,

evidence that can still be found

after a body has been burnt in the fire.

But none of these things were present.

And so one thing remains.

Could Tim have been poisoned or drugged?

We ordered an expanded panel,

which is a broad panel of various drugs and poisons.

Much to my disappointment, the first toxicology result

showed what we call therapeutic concentrations of medicines

that we knew he was on for his blood pressure.

That would not explain his death.

So we were still left with an uneasy feeling

that we had suspicious circumstances,

we didn't have a good explanation for his death,

so that meant we still had our work cut out for us.

'Without clear answers from the autopsy,

'the pressure was back on the detectives.

'And their concerns about Barbara's behaviour had been growing.'

Barb did not show any emotion.

"If you need anything, let me know, OK?"

Whether it was when I was initially speaking with her,

or after seeing Tim's body,

there was no emotion shown whatsoever.

Other people, throughout the day,

expressed that her behaviour was just odd

for someone that had just lost her husband.

'On the day of the fire,

'Mike noticed Barbara had posted a message about Tim on Facebook.'

I was Facebook friends with her. I saw the post.

I believe it said something to the effect of,

"Tim was a good father..." etc, etc, etc.

It was just a very strange post for someone to make

that had just tragically lost their husband.

'In fact, Barbara seemed very keen to get on with her life

'as quickly as possible.'

Barb, either the day of the incident or the day after,

contacted a local real estate agent,

advising that she would like to look at houses to move into.

'The biggest surprise came on the night of the fire

'when Barbara's 16-year-old son contacted the police.'

He'd reached out that he wanted to speak with me

about what had taken place that day at the residence.

He expressed that he had concerns that his mom, Barb,

may have been responsible for Tim's death.

'It was a shocking claim from a teenager,

'especially against his own mother.

'But he claimed his parents' relationship

'had been getting steadily worse in the previous months.'

He advised that they had not been getting along for quite a while,

that they had recently talked about getting a divorce.

He also advised that his dad had confided in him

that he believed Barb had tried to poison him with Benadryl

a couple of weeks prior to the incident.

He began writing notes, thoughts that came to his head...

...and provided those notes to me.

'As the police spoke to more members of the family,

'it became clear that life in the Pasa household was much more tense

'than it appeared from the outside.'

Barbara and Tim, at the time, lived together,

but through interviews we found out

that it was more of a divided household.

They were more roommates than husband and wife,

and just weren't getting along well at all.

'While Mike interviewed friends and family,

'Special Agent David Linkletter

conducted a detailed fire investigation.'

When we arrive at a fire scene,

we're gonna usually take a look from the area of least damage

to greatest damage.

We're gonna walk through the house

and just see what was going on during this fire.

'David soon confirmed what the local firefighters had suspected.'

'The only place where the fire

'could have started was the master bedroom.

'According to Barbara, it was caused

'by the candle she had lit on the morning of the fire.'

We evaluated the entire room

and we quickly discovered that, you know,

there was more going on than just a candle starting this fire.

The hallmark of fire investigations is really analysing burn patterns.

The burn patterns are gonna tell you where the fire occurred

and where it didn't,

and in this case we all were very concerned about the top of the bed.

There was a very distinct pattern on the headboard and the wall

that indicated there was definitely a fire in that specific area

burning for a much longer period of time

than anywhere else in this room...

...as witnessed by the extreme damage to the headboard

and the clean burn to the wall against it.

Usually the area that burns the longest

is gonna be the area where the fire originated.

'But could the candle have played any part in the fire,

'as Barbara claimed?'

The problem with that

was that that candle did not burn vigorously enough

to catch anything else in that room on fire.

It just sort of burnt that little area of carpeting

and really did not travel anywhere else.

'In this position, a lit candle could have caused a lot of damage,

'but David could see that it hadn't.'

All of the wood underneath that bed, next to where that candle was,

did not catch on fire.

There's less damage as you go toward the candle.

Burn patterns did not support the theory

that this candle started this fire.

It didn't happen.

'While no fire investigation is simple,

'investigators felt they'd found enough evidence

'to be sure where the fire had really started.'

We were confident the fire originated on the mattress.

The damage went from the top, in other words the mattress,

down and up and out.

This was obvious that the bed was lit on fire.

'That left a big question about Barbara's actions.'

'The investigators were beginning to wonder

'whether Barbara was trying to mislead them.'

Why would she point out this candle

in this room with all this damage in it?

How could she point that candle out right away?

We really felt, with all of the damage on the mattress,

and the little bit of damage that that candle did cause,

that that candle was deliberately placed onto the floor

and that fire damage was deliberately caused

in order to direct us, direct investigators in a different way.

In Iowa, police were investigating a case of arson and murder.

Tim Pasa was found dead at the scene,

but his body had revealed

that he had been killed before the fire even started.

Perhaps it held further secrets.

Prime suspect was his wife, Barbara. But what was her motive?

'The investigators knew that Tim and Barbara's marriage was in trouble,

'but they also discovered they had money problems.'

They were living paycheque to paycheque,

and Barb advised that she had an online spending problem.

They were looking at a divorce.

Barb was one who kind of liked a status in town

and didn't have the money, if they weren't married,

to live the lifestyle she was living.

'And the family's financial records revealed a recent change

'that struck the investigators as particularly significant.'

We discovered that, through Barb's employer,

that they had increased Tim's life insurance up to $200,000

in the last several months prior to his death.

'That suggested Barbara had a financial motive

'to kill her husband.

'But the investigators still didn't know how Tim had died.'

(Klein) Without another definitive cause of death,

there was going to be a lot more work to be done

in order to try to identify

what drugs and poisonings we needed to test for.

I did what a lot of forensic pathologists do,

and that is I pick up the phone and I call experts

who can help me take the case further on.

What other possibilities should we be looking at?

How do we expand our toxicology testing in order to try to find

what actually happened to Tim and caused his death?

And we're also going to need the help of law enforcement detectives

to also help us in what potential drugs we need to test for.

At the time of the incident,

Barb was a nurse at her local hospital.

She worked in the operating room and assisted with operations.

Which is very important information, because that then opens up medicines

that would not normally be tested for on toxicology screens.

So a second toxicology screen was performed

for more exotic or unorthodox substances.

And it was that when we received the result back of propofol.

Propofol is a very powerful anaesthetic drug

that's very commonly used during surgery in hospital.

It's a drug that very rapidly induces unconsciousness.

But it also lowers the blood pressure and suppresses breathing,

so it needs to be administered by a skilled anaesthetist.

Propofol is such a potentially dangerous drug

that it's even been used in assisted dying cases in Canada

and has been suggested as a drug

that could be used for executions in the United States.

But it's a drug that should only be found

in cases from a hospital setting,

so the finding of this drug in Tim's body

was a great surprise for the investigators.

(Klein) 'In my career, I've never seen this drug in a case.'

And we knew that Tim had not had any type of medical procedure

in which he received propofol.

'So how had such an unusual drug got into Tim's body?'

The most likely answer to that question

is that someone else injected the propofol into his body.

'Dr Klein now felt sure

'that Tim's death was not natural or accidental.'

And that finally left homicide,

in which a person dies at the hands of another,

and that fit very well

with the circumstances in my findings at autopsy.

'Dr Klein quickly told the detectives about his findings.'

It was bittersweet.

It was, "Now we know what caused the death,

but now we know more about the case and what has to happen."

In all the years I've investigated fires, this was the first

where we've proved the person was murdered prior to the fire.

It really confirmed to us

that this fire was more than likely started to conceal a crime.

'The investigators were now hunting for a murderer,

'and Barbara Pasa was their prime suspect.'

'They needed to find out

'if she could have stolen a lethal dose of propofol

'from the hospital where she worked.'

After using propofol,

a doctor or surgeon may not use the entire amount.

It is capable of just being thrown in a trash can.

There's no logging that needs to be done.

Barbara had very easy access to propofol.

It was her job to clean up those items used in a surgical room,

and she was also in charge of taking the trash

from the surgical room to the dumpster.

'Tim had been concerned for some time

'that his wife was trying to poison him.'

Tim had contacted one of his sisters,

a week or two prior, I believe,

told his sister, "Oh, by the way, I think Barb tried to poison me."

He didn't explain any further.

I believe that was the last text message that was sent.

'This seemed to corroborate

'what Tim's son had revealed about his father's fears,

'that Barbara was trying to poison him with Benadryl,

'an over-the-counter medicine

'used to treat allergies such as hayfever.'

I think if you were trying to poison someone with Benadryl

you'd need a lot of Benadryl, and they would notice the symptoms.

So you'd be tired, you'd become very dry.

It's an antihistamine.

Maybe Tim was noticing that over time.

'And the investigators found something else

'that might link Barbara to the fire.'

The master bathroom,

we found a grill lighter sitting on the countertop next to the sink.

Which we found a little odd,

for a grill lighter to be placed in that area.

She told police investigators she used that grill lighter

to light the candle that morning before she left.

'This grill lighter was a bit over-the-top to light a candle,

'but it would have been

'the perfect device to set light to the mattress.'

'The police now felt they had enough evidence to interview Barbara.'

(Moore) We were asking her several tough questions.

She knew that we knew something was suspicious

and criminal in nature.

The following day an ambulance call was made

from her mother's residence.

It was determined that she was suffering from an overdose

and she was immediately taken to hospital in Des Moines.

(siren blares)

I spoke with Barb and her mother

and determined that Barb had taken an overdose of insulin.

Barb was a diabetic.

She knew how to regulate her insulin.

I would say it was an intentional overdose.

'When Barbara was discharged from hospital,

'Mike was there waiting for her.'

(siren wails)

I think she was surprised to see us

outside the hospital when she was released,

but state law says that the medical staff had to advise us

when she was being released.

We immediately then placed her under arrest for arson and murder.

'When Tim Pasa died in a house fire in May 2018,

'his badly burnt body was still able to reveal the truth

'about what had happened to him.'

He'd been killed by a powerful anaesthetic drug called propofol

and then his house was deliberately set on fire.

The prime suspect for both crimes?

His wife, Barbara Pasa.

'Barbara Pasa was charged with first-degree murder

'and first-degree arson, nearly two weeks after the fire.

'It was a big shock for this small town.'

Since I've been with the department, since 2002,

this was the first murder that we've had in Centreville, Iowa.

'From the autopsy evidence,

'fire analysis, witness testimony and phone records,

'investigators pieced together what really happened

'on the day Tim Pasa was murdered.'

'Saturday May 5th 2018.

'By 6.30am, the couple's two children had left home

'to catch the school bus for their soccer tournament.

'Barbara told police she followed them in her car at 7.00am,

'but she had lied.'

It was determined that Barb actually left later

than she originally told us.

'7.08am, Barbara sent a text to her daughter

'saying she would be late.

'7.20am, a neighbour saw Barbara's car still parked in the garage.

'During this time Barbara must have disabled the smoke detectors.'

The first smoke detector was easy to tell.

With that door being opened,

we really believed that that detector was disabled intentionally.

The one located in the area of the fire was off the wall.

The battery was about three feet away from the smoke detector.

We were confident that that detector also had been disabled,

the battery had been taken out prior to the fire.

'This was also when Barbara must have injected Tim with propofol.'

It was the state's theory that she did poison him with the propofol

and then set the bed on fire

in hopes of covering up any evidence.

We really believe that the candle

was deliberately placed on the floor, burning,

to set the carpeting on fire,

but a separate fire was placed on the mattress

near her husband's deceased body.

That fire grew in much more intensity

and caused the damage that we had.

So the state's stance

was Barb used the candle as a distracter, a decoy,

to say that's how the fire started.

'Having killed Tim

'and, she believed, covered her tracks,

'only then did Barbara leave home.'

(Moore) Barb left the residence, went to a bank ATM,

which also had a camera on it.

We were able to secure evidence to show the timeframe for that,

which was around 7.26am.

'Several neighbours saw smoke coming from the master bedroom window

'of the Pasa home.

'They called 911.'

(sirens)

'Firefighters arrived just three minutes later.

'Neighbours desperately called Barbara but got no reply.'

(phone rings)

(Moore) She had received several missed phone calls, text messages.

She had reported that she was not able to receive those calls.

'But by tracking the cell phone towers

'her mobile connected to as she drove, investigators could show

'that Barbara deliberately missed at least five phone calls

from neighbours trying to warn her about the fire.'

(Moore) She finally, around 7.50, around 8.00,

responded to missed phone calls and text messages.

The thing that was very interesting to me

was that she spoke with the kids, she spoke with other family members,

but knowing that Tim was at the residence,

she never once tried to call Tim's phone.

'The investigators suggested

'that showed Barbara knew Tim was already dead.

'The investigators were satisfied Barbara had murdered Tim...

'...and the trial began on September 17th 2019.

'The autopsy evidence was critical.'

Having done a complete autopsy, reviewing his medical records,

and learning about the circumstances surrounding his death,

the most compelling and medically defensible cause of death

would be from propofol,

because there was really no other good explanation for his death.

I felt very comfortable that this was a homicide.

'The defence argued

'that the level of propofol found in Tim's blood was low,

'much less than you'd find

'in a patient being anaesthetised for surgery.

'But there is a good explanation for this.'

Propofol is very rapidly absorbed from the bloodstream

into the fattier parts of the body.

And there's quite a lot of fat in the human body naturally.

A lot of it's underneath the skin of the legs and the arms,

but there's also a large amount of fat inside the abdomen,

and a big sheet of fat that covers the bowel called the omentum,

and the drug will have moved from

the bloodstream into this fatty tissue.

But its damage will already have been done.

Its effect on the brain, its effect on breathing,

starving the brain of oxygen and causing death

will have taken place.

Because of the redistribution of the drug throughout the body,

it's not a surprise that only a low concentration was found

in the blood sample taken at the autopsy.

But that low concentration doesn't mean

that he wasn't injected with a fatal dose of the drug.

It had done its damage and then disappeared.

'In court, Barbara tried other arguments.

'She even suggested

'Tim might have been using propofol as a recreational drug,

'but it was easy to dismiss this theory.'

If he was someone who would abuse it,

the amount of propofol in his system,

there would have been a needle still in his arm.

He would have passed away that quickly.

There were no needles found in the location of the fire.

And it would be pretty hard to inject yourself

and then start a fire,

which appeared at this point to be intentionally set.

'But the defence tried to discredit the fire analysis as well.'

The defence really challenged me on the candle theory.

They really wanted that candle to be what caused this fire.

The defence was possibly blaming the dog

for tipping over the candle, which caused the fire.

When we take the totality of the situation,

it's hard to argue that that candle fell off the nightstand

and caused that fire.

That candle was deliberately placed onto the floor

and that fire damage was deliberately caused

in order to direct investigators in a different way

so that she could conceal killing her husband.

'After a week of evidence,

'the prosecution argued they had proved Barbara's guilt.

'Her motive was financial gain.

'Her means was the propofol she stole from her workplace.

'And her opportunity occurred that Saturday morning,

'while the children were on a school bus

'and she was alone at home with Tim.

'The jury deliberated for three hours.'

The jury came back with a verdict

of guilty on both arson first degree and murder first degree.

In the state of Iowa,

murder first degree is mandatory life imprisonment.

On the arson it is a 25-year sentence.

Barb will spend the rest of her natural life in prison.

'For a small Midwestern town,

'discovering that a well-known local nurse

'had abused her position of trust to murder her husband

'was very shocking.'

When Barb was finally convicted, it was relief.

It was relief for the whole community.

I hope it's something I don't have to go through again in my career,

but I'm glad we were able to use all our resources

and get answers for the family and for Tim.

But also knowing that things were still going to be hard.

Here we have two children that had now lost both their parents,

one to death and one to prison,

so that was... it was bittersweet on that aspect of it.

'The community rallied round as best it could.

'A fundraising campaign

'to help the children replace what they had lost in the fire

'smashed its original goal,

'raising $20,000 for them in less than a week.'

The children make me proud.

They've moved on. They have terrific adult lives.

Erm...

They're my kids. They're part of my family as well.

This was nearly the perfect crime, but bodies never lie.

And Tim's body had revealed

that he had been injected with a fatal dose of propofol.

If Tim had lived just a few more minutes,

his body would have eliminated all of the propofol

that Barbara had injected into him

and the evidence of his murder would have disappeared.

Even more shockingly, propofol is not a painkiller.

Tim could have suffered terrible pain as he burnt to death,

and Barbara, as a nurse, must have known that.

And that is what makes this such a terrible crime.

Subtitles by accessibility@itv.com