Original subtitles

The injuries were very catastrophic.

It was one of the more violent beatings that I think I've ever seen.

He was in the wrong place at the wrong time.

They had no enemies whatsoever, so why did this happen?

Would a daughter commit murder in order to achieve financial gain?

He admitted that they had not always been close.

Just the need to survive the addiction

can motivate extremely dangerous behavior,

including murder.

You hold out the hope that it's gonna be the,

the quote-unquote "smoking gun of the case."

Everyday in North America

dozens of people are murdered.

The key to solving the toughest of these homicides

lies in the final 24 hours of the victim's life.

To crack the case detectives must reconstruct that critical timeline.

The minutes and hours containing evidence

that can help unlock the mystery

and catch the killer.

Springfield, Missouri,

a city where residents are know for enjoying the simple pleasures of life,

from small-town hospitality to the great outdoors.

Springfield is in the heart of the Ozarks

We are surrounded by lakes and forest,

so it's very good if you're into outdoors.

It's good, good area for that.

It's kind of a bigger city with a small town feel.

If you move into a new neighborhood

people will bring cookies and brownies and breads, things like that.

It's a very warm and inviting place.

But as the sun rises on another beautiful day

it appears two Springfield residents have gone missing.

On my way to work I tried to call my mom

and I did not reach her.

I thought maybe she was in the garden

so I tried again a little bit later

and I still did not reach her.

My parents had a very strict routine

and I just felt like something wasn't right.

Her concern mounting,

Jessica and her fiancé Jason

rush from their home in Oklahoma city

to her parents' house in Springfield

five hours away.

We did that drive in about four hours that day.

Um, arriving at the house approximately seven o'clock.

I hit that garage door button

and both of their cars were in the garage.

I think my stomach just completely fell.

I knew something was very wrong

at that point in time.

Soon after arriving Jessica is calling 911.

When officers arrive, they go in and check the home.

And upon entering the home, immediately discovered

a male body upstairs in a hallway

They continued to search the residence

and in the basement of the home, in the office area

they also discovered another body.

The victims are identified as husband and wife of 30 year,

Gary and Jan Tyrrell.

My dad was a lifelong educator.

Um, he...

um, taught school.

He was a big teddy bear of a man.

He loved helping children, helping others

and my mom did as well.

Um, they both were huge givers.

My mom also had a big heart.

She loved to sew and crafts.

She knit little hats to make sure that

the cancer patients didn't get cold.

My parents were both very loving and kind people.

Tasked with investigating

the brutal double homicide of Gary and Jan Tyrrell

is detective Neal McAmis of the Springfield Police Department.

Gary had a lot of blood

about his head and shoulder area

with multiple gunshot wounds.

But there was nothing immediately within the areas of the body

that would indicate that the murder weapon was left on scene.

We also noticed there were some kind of weird flakes of some kind on the ground.

We didn't know what they were at that point.

With the position of Gary's body,

it was almost as if he was in a struggle with the suspect

trying to get away.

As if the suspect was grasping at him

and pulling at him to try to get him to come back

Jan had a very traumatic injury

to the back of her head.

And in my career was one of the more violent beatings

that I think I'd ever seen.

We did not know at that point

what the cause of that injury was.

But we did notice immediately

there were some of the same white flakes around her body as well

Jan's murder was really vicious, very violent.

Almost as if it was a rage type killing.

Gary having, what we believe, interrupted the crime.

He was in the wrong place at the wrong time.

In the middle of the living area of the basement

was a latex glove.

The Tyrrell home was extremely clean,

very well kept and organized.

So this latex glove was just totally out of place.

But of course you hold out the hope that it's gonna be

the quote-unquote "smoking gun of the case."

And that gave us some hope that we'd be able to find DNA on the glove

that could link us to the killer.

But we really don't know if this was a planned event

or if this was a crime of passion

and we don't know if there's one killer,

if we're dealing with multiple people.

We're still trying to piece puzzle pieces together

to figure out what we have going on.

To solve the double homicide of Gary and Jan Tyrrell

Detective McAmis will need to reconstruct

the final 24 hours of their lives.

At this point, we theorize the time of death.

It had been at least a while because the blood had dried

under both Gary and Jan.

The blood was dried on scene.

We believe the murders occurred

sometime between 7:00 p.m. and 7:30 p.m.

on the night of April 30th

The wounds inflicted on the victims in this case

tells me that this is not a well-executed or carefully executed crime.

There is some kind of message being sent

and, uh, that could be something internally expressive

that only the killer would know

but the brutality and the over kill

suggests that there was something very personal about this.

We're still looking for motive.

Gary and Jan are a very beloved couple.

So, why did this happen? Why-- What was going on?

With more evidence required to solidify a theory

Detective McAmis continues to search the house

looking for clues to catch the killer.

There was a large safe for Gary to keep his valuables.

It was really odd because there were pry marks on it.

Throughout the Tyrrell home, there's just

numerous valuables and collectibles of all kinds

from gold, jewelry, silver...

It was obvious to us that the Tyrrells were worth a lot of money

in terms of the collectibles and valuables that they had inside the home.

We found a ledger or kind of an itemized list of coins,

uh, that he was keeping track of

that were worth $22,000 total.

Gary was also a collector of guns.

Maybe the suspect grabbed one of Gary's guns and killed Gary with it.

Is robbery going to be our motive here?

Does the killer know the valuables and how much these items are worth?

But even with a possible robbery motive

detectives find themselves with little evidence

that could point toward their killer.

There's no type of forced entry,

there's no ransacking of the home

and we have no idea if anything is missing at all at this point.

The killer has to be someone that either, one, has access to the home

or two, it's somebody that Jan would've let inside the home.

Detectives turn their focus to the one person

they know who could get inside,

the Tyrrells' only child, Jessica.

In any circumstance

where you have a wealthy older couple

who are murdered together, you naturally have to ask

who would stand to benefit from this tragedy?

And police didn't have to look too far in this case

to see that their daughter stood to inherit everything.

In the horrific double homicide of Gary and Jan Tyrrell,

Detective McAmis has identified a person of interest.

The couple's daughter, Jessica.

The person who had the most to gain was me.

And because I stood to inherit everything.

Jessica said she last spoke with her mother at 3:20 p.m. on April 30th.

After speaking with her mother she had a doctor's appointment

and was at the doctor's appointment until about 5:00 p.m.

After her doctor's appointment,

she and Jason went to a Pizza Hut in Oklahoma city.

They arrived around 6:00 p.m. and ate dinner there.

And they arrived home at approximately 7:00 p.m.

Jessica said that Gary was supposed to teach a class that night,

from 5:30 p.m. until 9:00 p.m.

And then she would commonly

received a text message from her father wishing her, "Good night."

But she did not received a text message from her father on the evening of April 30th.

On the morning of May 1st,

Jessica tried calling her mother at approximately 7:30 a.m.

Her mother did not answer.

She's so concerned about not being able to speak with her parents,

that she wanted to come check on her parents to see what was going on.

It was odd as to why just can't Jason did not go into the residence,

was something more nefarious going on here

that Jessica and Jason possibly knew that the bodies

were gonna be in the home,

that they had some kind of involvement.

Detective McAmis shifts his focus

to confront Jessica about a possible financial motive

for her parents' murder.

She's the sole benefactor and would stand to gain

a large amount of money by the passing of her parents.

Jessica said that she didn't need her parents' money,

because if she wanted it that her parents would assist her and help her out,

so she denied any type of financial motive in terms of, uh,

wanting her parents dead.

With Jessica's motive under the microscope,

Detective McAmis moves on to interview her fiancé, Jason Murray.

When I realized that we were both suspects.

It was upsetting and it was also somewhat frightening.

Jason tells us that he went to work the morning of April 30th,

where he said he stayed until about 5:00 p.m.

We went to a Pizza Hut and had dinner.

And then returned home around 7:00 p.m.

which was in line with, with what Jessica had said.

We were able to confirmed through the surveillance footage at the Pizza Hut

that there is no way that Jessica or Jason could have been in Springfield

at the time of the murder.

It was readily apparent that they were not the killers of Gary and Jan.

Having established that Jessica and Jason

did not have the opportunity to kill Gary and Jan Tyrrell,

they are eliminated as suspects.

I did have a little bit of relief.

There was a lot of whispering that I could have been involved,

and knowing that...

you're a murder suspect does not, um, really sit well.

Investigators turned their attention to Gary's brother,

Larry Tyrrell.

We want to talk to Larry because it was reported to us that,

Gary and Larry were not always real close.

Is there some kind of animosity there between them?

We need to get Larry's story and information from him,

to see if he is a possible suspect.

Larry admitted that he and Gary had not always been close,

but had gotten much tighter over, over time.

Especially since the passing of their mother.

Larry said the last time he spoke with Gary,

Was about 7:00 p.m. on the evening of April 30th.

Viewing call records,

uh, on Gary's phone, it did show that Larry was being truthful

that they had spoken at that time.

Larry informed us he was in Mountain Grove on the evening of April 30th,

which his wife later corroborated.

Since Larry was an hour away in Mountain Grove.

He did not have the opportunity to commit the murders,

and is eliminated as as a suspect.

Based on the seven o'clock conversation that Larry had with Gary,

we believed that was the last known contact of, um, any kind with Gary.

We know now that Gary had left class early,

and that when he spoke with Larry at seven o'clock that,

the murders occurred sometime after that.

Detectives asked Larry if he knows anyone

who might have wanted to harm Gary and Jan.

Larry said Gary and Jan had no enemies whatsoever,

and could not think of why anybody would want to harm them.

He said the only motive he could think of would be financial.

My dad was big on diversifying.

He grew up poor, my mom grew up poor,

and so making sure you don't put all of your eggs in one basket

was very important to him.

So, my dad bought and sold

gold and silver and platinum,

weird collectable things you might see in a museum.

He was always looking for ways to make money

and it didn't really matter, what, how he did it.

Larry discussed some of the,

dealings that Gary was involved in.

In terms of the gold and silver trade.

Gary would often times do deals with random people

and he said he discussed with Gary the dangers of that.

Based on Gary's dealings, it is a possible scenario that,

he encountered someone that knew the valuables.

Could it have been somebody that

followed him home, could it have been somebody that had staked him out

and potentially was going to burglarize the residence?

In the double homicide of Gary and Jan Tyrrell,

Detective McAmis is working a new theory.

Could the killer be connected to Gary's side business of trading gold and silver?

Larry notified us of a close business associate of Gary's.

They would often conduct transactions together.

Harold was not only a business associate, but also a close friend that Jan

would've allowed access to their home.

Harold knew how much Gary was worth

and what Gary was in possession of at the residence.

In Gary's phone records, we found that Gary placed a call

to his business associate

at 6:57 p.m. on April 30th.

We were able to speak with Harold and he told us that he was in Mountain Grove

at the time the incident occurred which later on proved to be true.

We were able to eliminate him very quickly based on that.

With Gary's friend and business associate ruled out.

Detective McAmis finds himself running out of leads.

We're trying to look at all angles to figure out exactly

who would have the means and opportunity to commit this crime

uh, it's a frustrating process

having to go down the different avenues,

but we have to check all the boxes and make sure

that there is no stone left unturned.

It's a very hard pill to swallow,

even though you know and understand that law enforcement

is doing their job.

I really just wanted them to move on to actually, "Who did this?"

I really had to put our faith in the justice system and that,

the justice system would do us right.

But then, Detective McAmis finally catches a break.

The DNA from the latex glove showed to have male characteristics.

So, we now know that we're dealing with a male suspect.

But when checking the DNA from the glove,

in the DNA database,

there was no match.

Detective McAmis goes back to the drawing board.

Looking for any new clues that could lead to a male suspect,

who had access to the Tyrrell home.

When speaking with Larry about who had access to the Tyrrell home,

he said, it was just a very select few people, a couple of close family members

and he also said Gary's best friend Mark Porter.

Mark was frequently visiting the Tyrrell residence,

Mark would have had knowledge of the valuables that were inside the Tyrrell home.

Gary was mentoring Mark with the gold and silver trade.

My dad did not have a lot of close friends and so I really thought it was great

that he had someone he could do things with.

Detective McAmis invites Mark Porter

down to the station for an interview.

Okay.

My first impression of Mark Porter was,

he was obviously a very intelligent individual,

but at the same time he was also extremely arrogant.

Almost to the point of being pompous.

Um, there was no doubt that he thought he was

the smartest person in the room.

Mark told us that he and Gary, um, met each other

in the Mountain Grove school district

where Mark was the superintendent of schools

and Gary was his assistant.

Mark's initial description of his relationship

with Gary was very odd.

He described him as just being more or less acquaintances.

That was really disheartening

because my dad definitely felt like,

Mark was his best friend.

When Mark kind of down played the relationship

and put it off as just kind of

being acquaintances, that was definitely a red flag and alarming to us.

I think most people want to downplay their relationship to the victim,

especially if they are in fact considered suspects.

The belief or the idea that somehow you're throwing

the investigators off the scent,

um, it's something that I think a lot of people will utilize as a ploy

to distance themselves from an investigation.

Detective McAmis asks Mark about his whereabouts

on the night the Tyrrells were murdered.

On the day of April 30th, he went to work very early at approximately 5:30 a.m.

He said he worked at IBM throughout the entirety of the day.

At 7:45 p.m. Mark said he left to meet Gary at a local McDonald's at eight o'clock.

Where he said he waited for about 45 minutes for Gary.

When Gary did not show up for the meeting at McDonald's,

he went on ahead and just drove to the Tyrrell residence.

But said he, he could not get any answer of any kind,

he said, he didn't notice anything wrong,

and so after leaving the Tyrrell residence.

He went back to work,

he said he arrived at approximately 9:15 p.m.

But we were able to confirm through Mark's brother that he had in fact seen Mark

arrive at the IBM office at approximately 9:15 on the night of April 30th.

We were able to eliminate him very quickly based on that.

With Mark Porter cleared in the double homicide of Gary and Jan Tyrrell.

Detective McAmis is back to square one in the investigation.

It's very frustrating in cases with DNA

whether there is no offender match in the database,

and unfortunately you have to sort of sit and wait until

that offender gets arrested for something else and the link gets made.

With CSI having finished processing the crime scene,

police release the Tyrrell home to Jessica.

Being...

in their house,

and...

they were not there,

and they were not coming back,

was incredibly hard.

Jason and Jessica went throughout the home

trying to identify anything that could be missing.

A couple of ivory tusks were missing from the basement.

Based on the location and the composition of the material

that we found around both of the bodies,

that led us to believe that the tusk was possibly used as a murder weapon.

Jessica pointed out to us that her father often kept a tub of coins

next to his desk

and she said the coins were missing.

During the processing of the scene,

we located a coin ledger that Gary had.

The list indicated that he had over $1,330 in face value coins,

but the coins were worth approximately 22,000 dollars.

Mark Porter would have obviously known

that those coins would have been much more valuable than just the face value.

Based upon our findings,

we're gonna definitely have to take a much harder look into Mark Porter.

After discovering the theft of Gary Tyrell's silver coin collection

and a possible murder weapon.

Detective McAmis is zeroing in on a previously cleared suspect,

in the double homicide of Gary and Jan Tyrrell.

Gary's close friend, Mark Porter.

While speaking with Larry again,

he seemed bothered by something.

Larry got really stern with me and very focused.

He told me that he was very suspicious of Mark Porter.

Larry informed us

that Mark had a severe gambling problem.

He told us that Mark should be a very wealthy individual

because he has a very lucrative job at IBM,

making a lot of money, and is extremely successful.

But Mark had asked for a quarter-million-dollar loan from Gary.

Larry just thought that was preposterous

and said Gary was not gonna give him that kind of money,

and was shocked that Mark would even have the audacity

to ask for such a sum.

People who gamble

often times have impulse control problems,

or problems in terms of their thinking.

They don't see their wins as independent events,

they see themselves on a lucky streak.

And if you're thinking

in cognitively distorted ways like that,

it may not be so much of a leap

to think that you might resort to violence

to repay your debts.

If Mark is in debt

to that point to where he's needing to request

a quarter of a million dollars from Gary,

it could obviously put some strain

and give motive for these crimes.

It was told to us that Mark was a very religious man,

a family man.

Obviously very intelligent.

But in digging further,

when we spoke with past co-workers

and other people that knew Mark,

uh, there was a different picture that was being painted.

With this new information,

Mark Porter goes from being a friend of the Tyrrells

to being their possible killer.

To build their case,

detectives start digging into his background.

We were able to locate evidence

that showed Mark Porter had gambled

hundreds of thousands of dollars,

uh, throughout a several-year time period

at various casinos.

We also found that

that Mark was in some serious financial difficulty.

Mark got rid of a Lexus they had,

and we also saw where he had sold

a motorcycle that he was in possession of.

Having established

that Mark Porter had a clear motive...

investigators need to prove

whether he had the opportunity to kill the the Tyrrells.

Looking for answers,

Detective McAmis brings Mark's brother and boss, Bruce,

in for questioning.

When we asked him about Mark's gambling issues,

he almost seemed put off

and surprised and shocked

that we would even be talking about such a thing.

Mark was above that, that he was far too good,

and said that Mark was not a gambler of any kind.

For his brother not to know

of the gambling issues going on with Mark,

it was readily apparent to us

that Mark was leading a double life.

Investigators question Bruce

about seeing Mark at the office around 9:00 p.m.

He confirmed that he, in fact, did see

Mark at the IBM office.

He arrived at about 9:15 that night.

What he told us that was a little different than Mark was,

he said he had actually got in to the office before that,

had seen some of Mark's belongings,

and that Mark was gone

for approximately 45 minutes.

Mark had not told us that.

Mark said that he arrived at the office,

and said that his brother just happened to drive by.

So, there was a little discrepancy

in their scenarios right there.

Right now, there's a whole bunch

of circumstantial evidence pointing towards Mark

as being our prime suspect, without a doubt.

The problem is, is we have

no hard physical evidence on Mark to this point.

With the evidence stacking up against Mark Porter,

Detective McAmis hauls him down to the station

for another round of questioning.

Mark denies both the loan and gambling issues.

At one point, he finally admits

that he gambles a little bit,

but he says that it's no big deal

and that it's not a problem.

And essentially played that off as

money is not an issue.

So, we asked directly

if he had any involvement in the crimes.

And he denied anything to do with it.

The fact that Mark presents as this successful business man

and yet ends up immersed in this horrible tragedy,

speaks to just how insidious

and dangerous a gambling addiction is.

I mean, just for the need to survive the addiction, um,

can motivate extremely dangerous behavior

up to and including murder.

Detective McAmis redirects,

and asks Mark when he was last inside the Tyrrell home.

Mark told us that

he last time he was at the Tyrrell home

was on the Monday before the crime,

which would have been just a couple of days previously

to when we believe the homicides occurred.

So, we asked Mark to submit to a DNA sample.

And he was immediately stand-offish about that

and that he would need to speak with a lawyer

before he'd be willing to give us a DNA sample.

It was a huge, huge flag for us. Very alarming.

We're trying to solve the murder of his best friend,

and here he is, he's not willing to cooperate.

It was quite the telling sign right there

that Mark had something to hide.

Investigators have their prime suspect

in the brutal double homicide of Gary and Jan Tyrrell...

Gary's close friend, Mark Porter.

But without a matching DNA sample

to directly link Mark to the murders,

Detective Neal McAmis searches for more evidence,

and finds it in a surprising place.

The investigator that

decided to look for Mark in the pawn database,

it was a brilliant move on his part.

Mark had sold approximately $1,321 worth of coins.

It was close to the amount of face value

that was listed on Gary's ledger that he had.

But when we, in fact, went to

view the transaction at the coin shop,

we found out that Mark was actually paid

over $18,500 for the coins,

which is right in line

with what Gary had listed on his ledger.

The owner of the coin shop confirmed that, in fact,

he did do a large transaction of coins

on the day after the bodies were found.

The owner of the coin shop also has surveillance footage

which indeed showed

Mark Porter in the coin shop doing the transaction.

And Mark Porter was wearing the same

clothing he had on whenever we interviewed him,

shortly after he did the selling of the coins.

As intelligent as Mark is,

it was very apparent, just his stupidity,

when it came to criminal acts.

Even though we have the coins,

we still needed something a lot more solid

in terms of physical evidence to proceed with the case.

We know that we are

somehow going to have to obtain Mark's DNA.

To obtain Mark Porter's DNA,

Detective McAmis organizes a large undercover task force.

We put undercover officers,

uh, maintaining surveillance of Mark for weeks at a time,

to try to somehow

discreetly get his DNA without him knowing.

We're looking for any type of article

that Mark might handle

uh, or use that would produce his DNA.

During this time,

narcotics investigators are relaying to us

that Mark's behavior is very strange and odd.

He would go into a restaurant

and he would not leave anything behind

for them to obtain,

and it was becoming very challenging

for our undercover officers to try to get his DNA.

After weeks of surveillance,

Detective McAmis finally catches a break...

when Mark Porter visits a lube shop for an oil change.

One of our undercover officers

went in and got an oil change with him.

Mark had been drinking from a coffee cup.

And when Mark's vehicle was finished,

Mark put the coffee cup down and left it behind.

Our undercover officer immediately seized the cup.

And we transported it directly

to the Missouri State Highway Patrol lab for testing.

Less than 24 hours later, we had our match.

It is confirmed

that Mark's DNA is a match of that

that we found on the latex glove

that was located in the Tyrrell home.

The feeling of elation was...

it's almost indescribable.

We knew that we were gonna be able to bring

some kind of closure to the Tyrrell family

along with being able to put away

a very violent and vicious man.

Detective McAmis is now able to piece together

Gary and Jan Tyrrell's final 24 hours.

Mark knows that Gary is supposed

to teach a class that evening

from 5:30 until 9:00 p.m.

Approximately 5:30,

Mark went to the Tyrrell residence...

knowing that she would have been a roadblock.

We believe that Jan turned down

Mark's loan request.

And it was at that point Mark snapped.

Consumed with rage,

Mark Porter grabs a walrus tusk

from a nearby table and attacks Jan.

After Mark kills Jan,

we believe that he was looking throughout the home.

He would've had knowledge of the valuables.

Gary let class out early that night

shortly before 7:00 p.m.

It's right after that when Gary has a conversation

with his brother Larry.

We believe that Gary went home

shortly after that conversation.

And that's when he interrupted Mark's crime-in-progress.

Mark possibly grabbed one of Gary's guns.

He runs upstairs.

And there's the confrontation

right at the top of the stairway.

Fired a couple shots at Gary.

And then Mark proceeded to beat Gary

as he lay on the ground.

Mark gathers up

the belongings, the walrus tusk,

the murder weapon in terms of the gun,

and the items that he stole.

He left the house,

even locking the door after he left,

and fled the scene at that time.

There was never any indication

of any type of remorse whatsoever.

There was never an apology to the family.

Nothing at all to indicate that Mark felt bad

about what he did.

Throughout, he continued his arrogance and pompousness

and it just speaks volumes of the type of individual

that Mark really is.

With the viciousness of the crime

and the lack of remorse,

Mark is most definitely a sociopathic type.

Mark's narcissistic behavior

and constant need to lie to people,

uh, to show that he was

successful and wealthy and capable,

um, came shattering down around him,

um, when his gambling debts caught up to him.

I don't necessarily know that he went there

planning to commit murder,

but I think it was a perfect storm.

Mark Porter is charged

with first-degree murder

in the deaths of Gary and Jan Tyrrell.

He pleads guilty

and receives two consecutive life-sentences.

Arresting Mark was most definitely

one of the highlights of my career.

Being able to bring some closure

to the Tyrrell family

was just an indescribable feeling.

I hope that

the family gets some sense of justice

knowing that this vicious, brutal killer

will spend the rest of his life in prison.

I miss most...

just them being here.

Their support. Um...

They were always a phone call away.

Despite the tragedy of losing her parents,

Jessica Tyrrell

continues to work to honor their memories.

I would like my parents to be remembered

as warm, loving couple

who helped so many people.

They made a difference in the lives

of those around them.