[piano music playing]
The internal organs looked like the cells were actually killing themselves.
[gasps]
The difference in cases of poisoning is these are invisible murders.
[Tony] Who was within her circle?
Who would have physical access to her?
The bed was barely cold
before there was another woman in bed with him.
[Laurie] There was a fight.
It was a hard pill for us to swallow,
that he couldn't kill his mother.
[gasps]
Whoever wrote that letter was behind the homicide of Mary Yoder.
There's no doubt about it, it was almost the perfect crime.
[narrator] Every day 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.
Whitesboro, New York,
a suburban enclave in Oneida County
where families and business professionals can thrive.
Whitesboro is a very stereotypical suburb,
little more than three hours outside of New York City.
It is extremely diverse
for something that is so small.
The village of Whitesboro's a small community.
Usually everybody knows everybody.
Very low crime rate.
They have their own police department.
[Tony] In Whitesboro, homicides are incredibly rare.
I'm not sure I can, off the top of my head,
think of one of the last homicides occurred in Whitesboro.
[narrator] But while most residents are enjoying
a quiet Tuesday morning commute,
William Yoder brings her wife Mary
to Saint Luke's Hospital
under mysterious circumstances.
[Mark] On July 21st, Mary arrives to the hospital
complaining of stomach issues,
she's been puking, diarrhea for the past 18 hours.
Doctors have no idea really what's going on.
In the middle of the night she went into cardiac arrest.
And they revived her.
Numerous tests were ran in the hospital.
They still weren't able to determine
what was causing her to be so sick.
That afternoon, on the 22nd at around 2:54,
after having gone into cardiac arrest about seven times,
Mary Yoder finally succumbed.
[beeping]
[narrator] Mary's death leaves her family and doctors
asking the same question,
"How could a seemingly healthy woman die so suddenly
with no known prior illnesses?"
[Laurie] Marie Yoder was a full of life,
vibrant woman in her early 60s.
She was married to William Yoder
for approximately 40 years.
They had three children, Liana, Tamryn and Adam.
[Mark] Mary and Bill were both licensed chiropractors
in New York State,
they owned their own practice.
Everybody describes Mary as a kind, caring person.
No enemies, no people that disliked her or she would dislike them.
Marie Yoder was an extremely healthy woman for her age.
She had a very healthy diet.
She took a lot of supplements and a lot of vitamins
and led a very active life.
Her death was obviously perplexing to the doctors
as it's not a person with chronic disease or chronic illness.
Obviously, there was a lot of emotional trauma involved with the family.
I mean, this is totally out of the blue,
this a shock to everybody.
[narrator] Because Mary is under hospital care
when she dies, an autopsy is ordered
by the Onondaga County Medical Examiner's Office.
[Mark] One of things that Dr. Clark who performed the autopsy noticed is
that the internal organs looked like organs
of a person receiving chemotherapy.
The cells were actually killing themselves.
So that let them to believe, obviously,
there were some foreign chemical or substance
that may have been responsible for this death.
[narrator] Heading up the investigation into the suspicious circumstances
surrounding Mary Yoder's death
is detective Mark Van Namee
of the Oneida County Sheriff's Office.
The Oneida County Sheriff's Office, myself,
received a phone call
from Mary's youngest sister, Sharon, stating that,
her sister had passed away. Can you guys look into it.
When Dr. Clark ordered the first section
of toxicology
on Mary's blood from the autopsy,
he checked for the typical heavy metals in poisons
that could have possibly been.
And that came back negative.
He then reaches out for poison control,
and he speaks with the Dr. Jeanna Marraffa.
[Laurie] Dr. Marraffa reviewed all of Marie Yoder's medical records
and she recommended that Dr. Clark test
for something called Colchicine toxicity.
It came back that Mary Yoder had extremely high levels
of colchicine in her system.
The cause of death was ultimately ruled
death by colchicine toxicity.
[Mark] Her stomach contents also came back positive for colchicine,
which let us know that this substance
was orally ingested not injected into her vein.
Colchicine is typically used to treat gout.
It would typically take about 60 pills
to kill somebody of Mary's size.
However, when you buy it in the pure powder form,
you could balance a lethal dose of colchicine
basically on the end of a tooth pack.
There was nothing anybody could do to save this lady.
Not one thing.
There's no antidote for colchicine.
So, as we're moving forward in the investigation,
we start to realize that we're dealing with a homicide.
[narrator] To find out who poisoned Mary Yoder,
investigators will now need to piece together
her final 24 hours.
Once we learned that the colchicine was ingested,
it became important to us to try to figure out
what Mary had to eat or drink that day.
The timeline for one to see effects on Colchicine in their body
is anywhere from four to eight hours after ingestion.
Based on when Mary Yoder started to exhibit symptoms around 4:30,
she could have been ingested this anywhere
between 8:30 in the morning and 2:30 in the afternoon.
That's the time period
of opportunity they have to look at
to see who had access
to anything that Mary Yoder might have drank
or eaten at that time,
and those are the people that we need to look at
as potential suspects in this case.
William Yoder advised the investigators
that Mary started developing symptoms
while she was still at work,
so they obviously wanted to interview
anybody that was working with her that day.
[narrator] Having stablished that Mary was poisoned
between 8:30 a.m. and 2:30 p.m.,
investigators contacted the office manager of her clinic,
Kaitlyn Conley, to find out more about her schedule.
[Laurie] Through the investigation,
we learned that Kaitlyn Conley
was the on-again-off-again girlfriend
of Mary Yoder's son, Adam Yoder.
Back in 2011 or 2012,
Adam was able to get her involved
in the family business, and then ultimately
Kaitlyn took over as the office manager
at the Chiropractic Family Care.
Kaitlyn Conley is an important figure in this timeline
based upon the fact that on the date Mary becomes ill,
Kaitlyn is with her
from the minute she walks in the office until she leaves.
Kaitlyn does state that Mary left for a lunch period
from approximately 12:30 to 1:30.
[Laurie] Mary was going to go have lunch with her mother,
but by the time she got to her mother's home,
her mother had already had lunch.
So, when Mary got back at around 1:30,
she prepared a protein shake for herself
which was something that she had quite often for lunch,
and she took some supplements.
Once she got that down,
she began to see her afternoon patients.
And then, at around 4:30 in the afternoon,
Kaitlyn noticed that Mary wasn't herself,
Mary was going back and forth to the bathroom.
And then, when Mary left work at around 6:00,
she had advised Kaitlyn
that she was feeling quite ill.
So, based on that,
the investigators were able to work backwards,
and the strong feeling was that
she probably ingested the colchicine
at the same time
she drank the protein shake at lunch time.
[Mark] And that is the only thing we know
that Mary Yoder has to eat or drink
from eight o'clock in the morning
until she started showing symptoms, about 4:30 p.m.
[narrator] Having determined Mary's lunchtime protein shake
was spiked with Colchicine,
investigators need to confirm who was at Mary's office on July 20th.
[Mark] When you're dealing with a poisoning case,
you need to determine a timeline,
obviously you gotta talk to the people around your victim that day.
[Laurie] They got a hold of Mary Yoder's schedule
and made contact with every single patient and interviewed them.
Basically, they described her as somebody that everybody loved.
We didn't find any that were unhappy with Mary
or that there were conflicts with.
[Tony] Looking through Mary Yoder's devices
there are no communications, saying that someone has
a problem with Mary Yoder or someone's threatening her.
[Mark] So, were pretty comfortable that whatever happened
wasn't the result of an unhappy or upset client.
[narrator] Without a clear motive,
detectives are left wondering who would want to kill
such a beloved woman as Mary.
Who are within her circle?
Who would have physical access to her?
Who could have actually poisoned her?
[Michael] The difference in cases of poisoning is
these are invisible murders.
This is someone who would've had access to the victim
that suggest some kind of trusting relationship
between victim and offender.
[Keira] There's lots of premeditation involved here.
Even to be able to know what type of poison to use,
to know where to get that from,
how to purchase that, and how to conceal it.
This person has clearly done lots of thinking
in regard to this method of murder.
Odds are, this was committed
by somebody who knows her well, and the question is who.
[narrator] In the investigation into Mary Yoder's homicide,
detectives believe the mother of four
was poisoned by someone close to her.
Their search for suspects
begins with her husband, William Yoder.
When you have a homicide that involves a husband or a wife,
obviously the spouse is gonna be a main focus.
I don't know the exact stat, but a high percentage
if a husband or wife is a victim of a homicide,
often the spouse is the one responsible.
You don't wanna go interview the main suspect
without all the background information possible.
[narrator] To help build their case,
investigators ask William and Mary's eldest daughter, Liana,
for more insight into her parents' marriage.
Liana describes they were a very happily married couple,
extremely devoted to one another.
They've been married for 40 years,
and when she died so suddenly,
he actually advised his daughter Liana
that he didn't think that he could go on living without his wife.
But she knew her aunt,
Kathy, one of Mary Yoder's sisters,
had just lost her husband a year prior
and strongly suggested he reach out to Kathy
and maybe that would help.
Ultimately, they struck up a friendship
and that friendship became a romantic relationship.
[narrator] This new revelation about William's romantic life
comes as a surprise to investigators.
[Roots] William had taken up with his sister-in-law
some short weeks right after the death of his wife.
So, that would've raised a significant concern for investigators.
The bed was barely cold
before there was another woman in bed with him.
[Laurie] Could William Yoder have had a relationship with Kathy
prior to the death of Mary Yoder?
Then decided that he wanted his wife out of the picture?
Could he have possibly been responsible
for administrating colchicine to his wife that day?
Investigators are interested in William Yoder's timeline
because they want to know at what point
he had access to his wife and any food or drink
that she may have been ingested that day.
[narrator] With suspicions swirling around William Yoder,
detectives bring him for an interview.
They start by drilling down on both,
his and Mary's timelines leading up to her death.
[Laurie] On July 20th, William Yoder got up around 6:00 o'clock.
He does exercises and he's the one
that usually gets breakfast ready for himself and Mary.
[Mark] He indicated that nothing was out of the ordinary
on the day she becomes ill.
She woke up at her normal time,
wasn't complaining about any kind of symptoms or anything like that.
[Laurie] She grabbed a quick breakfast that morning
that her husband prepared for her,
ran off to work at 8:30
and would've normally been done around 5:00 or 5:30 in the evening.
We know that Colchicine was in either the supplement
or the protein powder shake that Mary Yoder drank
around 1:30 that afternoon.
[Mark] William reported to us on July 20th he had a typically day off,
reading, watched a movie,
he basically spend the day at home by himself.
[Laurie] Mary left Chiropractic Family Care
feeling extremely ill around 6:00,
and around 6:30 she arrived at her home.
For the rest of the night, she remained on their couch.
William advised investigators that during that evening,
she spent the time continuously going back and forth to the bathroom
with diarrhea and vomiting.
[Mark] Early the very next morning,
William reaches out for their daughter Liana,
who's a doctor in Long Island.
It is at that point, Liana is like,
you probably should take mom to the hospital,
she's not any better,
it sounds more serious than the typical upset stomach.
[narrator] Once at the hospital,
Mary's condition continues to deteriorate.
In the middle of the night, she starts having cardiac events.
Where she's revived through electronic shock,
and eventually after six or seven of these incidences,
she passes away at roughly 2:50 the next afternoon.
[machine beeping]
[narrator] Detective Van Namee then shifts course
and asks William about an odd note he found
in the initial police report.
[Laurie] Before she went into cardiac arrest,
William Yoder left his wife's bedside
on the night of July 21st
because his wife wanted him to go,
she needed sleep, and she knew that
he was going to be covering her patients the following day.
[Michael] It's after he goes home
that her conditions deteriorates even further.
So, the hospital reaches out for William
in the middle of the night.
He does not hear the phone calls,
so the hospital actually reaches out to the state police
and sends a state trooper
to William's house to knock out the door,
and alert him that there's a problem at the hospital.
I think common sense dictates that
if you have a loved one who's in the hospital,
then you're gonna have your phone with you at all times
in case the hospital or your loved one wants to reach you.
The fact that William Yoder went home
and put his cellphone in another room
and made him essentially unreachable
was an issue that we had to contend with.
[narrator] Investigators question if Williams mysterious behavior
was influenced by his new relationship
with Mary's older sister, Kathy.
[Mark] We're trying to determine when this relationship started
so, we need to speak with Kathy.
She was fully forthcoming and provided us a deposition,
gave us free access to anything we wanted, phone records.
She wasn't trying to hide anything.
[Laurie] After an extensive interview with Kathy,
they were able to determine that there was really
no real relationship between Kathy and William
prior to the death of her sister Mary.
It started because these were two people
who had lost their significant others
and found some companionship in each other.
They determined the relationship between William Yoder and Kathy
is just not an issue in this case.
[Mark] William and Mary had been together 40 years.
They ran a business together. They had three kids together.
There's no indication that there was marital problems
that would've led to Mary's demise by poisoning.
[Laurie] Based on that information,
William Yoder is probably not a suspect in the killing of his wife.
[narrator] With William ruled out,
investigators are back in the hunt for their next suspect.
[Tony] The investigators involved
have to consider all possibilities.
All potential suspects who would have access, who would motive.
The use of poisoning as a weapon
can tell us a lot about an offender's mindset.
This is not a frenzy crime.
This is not a crime committed from ambush.
This is something often slow, methodical, and silent.
[narrator] Then, out of nowhere,
the case takes a surprising turn
when investigators receive a pair of anonymous letters.
[Laurie] On November 23rd, 2015,
both the Onondaga County Medical Examiner's Office
and the Oneida County Sheriff's department
received a typed written anonymous letter.
[Mark] The letter clearly points that Adam Yoder,
William's and Mary's youngest son,
is the main suspect.
It talks about why Adam Yoder
would have the motive to carry this out.
That he had financial means to gain by this.
It also talks about how he purchased the Colchicine.
It was almost as if it was too good to be true.
[narrator] In the homicide by poison of Mary Yoder,
a beloved mother and chiropractor,
detectives have received two anonymous letters
that claim to know the identity of her killer.
Mary's own son, Adam Yoder.
[Mark] When we received the anonymous letter,
we were guarded about, you know,
how much faith we put in this.
[Laurie] One of the reasons why get anonymous tips
or anonymous letters is the person either doesn't want to get involved
or somehow is involved
and doesn't want their identity known to law enforcement.
[Mark] The person who's writing that letter
has way to much knowledge of this case
and specifics of this case to not be involved.
The letter talks about why Adam Yoder
would have the motive to carry this out.
That he had financial means to gain.
It also talks about how he purchased the colchicine,
and that we're going to find the bottle of colchicine
under the passenger seat of Adam Yoder's car.
The person writing this letter
has an immense knowledge of this crime.
So, one of my main goals was to figure out who wrote the letter.
The letter we received is typed on a computer,
there's no handwritten marks on it, no return labels.
No indications about where this may have came from.
[Laurie] But there's a stamp on it.
Obviously, they're interested in determining
whether if they can find any DNA under that stamp
that might lead them to the person who wrote his letters.
[narrator] While investigators wait for the results of the DNA testing,
they dig into Adam Yoder's background.
[Laurie] It was a hard pill for us to swallow
that Adam Yoder could in fact have killed his mother.
But clearly based on the information that was in the letter,
we had to include Adam Yoder
as a person of interest in this investigation.
We learned that Adam had some issues.
He worked on-and-off, he went to school on-and-off,
he wasn't financially independent at this point.
Adam was the youngest and he was the only son,
and I think his mother was super protective of him
and coddled him a lot.
But there's was this allegation that there's was a fight
with Adam and his mother, that he was upset,
and so, supposedly he took some of her supplements
and put colchicine
on the supplements or in the supplements.
And that's how Mary Yoder ingested colchicine.
[narrator] With the possible motive stablished,
investigators called Adam down to the station for questioning.
And lo and behold, not only did he respond immediately
to the sheriff's department,
but it actually came in the vehicle
that the anonymous letter writers said
the murder weapon could be found in.
[Mark] When Adam arrives at the office,
I am the one who interviews him.
When he sat down, I told him, make no mistakes about this,
we're investigating the homicide of your mother.
[narrator] Investigators grill Adam about his whereabouts
in the days leading up to his mother's poisoning.
[Laurie] Adam Yoder advises the investigators on July 15th,
five days before Mary Yoder ingested the colchicine,
he went to Long Island
where his sister Liana lived and stayed with her.
She had four young children. They love their uncle.
He was a sort of the building babysitter.
And the only reason he left Liana's home on that day
is because he found out that his mother was ill in the hospital.
And then ultimately, they brought up to him,
the fact that they had received this anonymous letter.
At that point, he didn't necessarily believed
that this was really true,
and then investigator Van Namee showed him portions of that letter
that said where in the vehicle
the murder weapon could be found.
At that point, investigator Van Namee asked Adam Yoder
if he would be willing to have them search his vehicle.
Adam was skeptical and wanted to speak to a lawyer,
which is absolutely his right to do so.
[narrator] Investigators set Adam up with a public defender
and after speaking in private on the phone,
Adam agrees to let detectives to search his car.
[Mark] I wanted Adam out there,
because if we pulled out what was potentially the murder weapon,
I wanted to see his reaction.
We're outside at the sheriff's office, he's smoking a cigarette.
Investigator Simmons pulls out the bottle labeled colchicine.
And I can remember this, and I'll probably remember it forever,
the cigarette almost fell out of the corner of this mouth.
Like he was in such shock at what he just observed.
[Laurie] And in addition to the colchicine
and probably more importantly, they find the receipt
for the purchase of that colchicine.
The receipt indicates
there's a Gmail account used to buy this colchicine,
and that's address is MrAdamYoder1990@gmail.com.
[narrator] But something about the evidence
doesn't sit right with the investigators.
[Laurie] If I'm responsible for committing a crime,
the last thing I'm gonna do is drive to a law enforcement
with the murder weapon in my vehicle.
I'm just not gonna do that. Doesn't make any sense.
[Mark] This is not hard to dispose of.
If he was responsible,
we were certain that this would have been gone.
[Michael] The fact that the purchasing
and the poison used in this case
was associated with the Gmail account in Adam's name
isn't necessarily a smoking gun.
Anybody can create any digital identity
in anybody else's name.
So, it's very easy to misdirect police
and effectively digitally frame somebody for a crime.
[Lauri] When Adam is shown the address
he indicates it almost looks like it's a combination
of two e-mail accounts he has.
But that is not one that he's ever seen or ever created,
and law enforcement has no reason to disbelieve him
based on everything else they've learned from him.
[narrator] Even though the evidence suggests
Adam is being framed for his mother's murder,
investigators need more information to prove he wasn't involved.
So, in my mind he becomes maybe our best witness.
And I make it very clear to Adam,
as we're back in the interview room,
that if there's something he's not telling us, we need it now.
Because it's obvious somebody's out to get you
and we need to try to figure out who that is
as quickly as possible.
[Laurie] Obviously, whoever was the author of that letter
was wanting to point the finger
and wanting the investigation to go
in the direction of Adam Yoder.
So we were very interested in finding out who that person was.
They don't wanna be known.
Whoever wrote that letter
was the person who was probably
behind the homicide of Mary Yoder.
[narrator] In the mysterious murder of Mary Yoder, investigators believe
the author of the anonymous letter is their main suspect.
But who stands to gain from framing Adam Yoder from his mother's murder?
[Mark] This is an absolutely crazy case,
but the thing you've gotta remember in all investigations
is you go back to basics.
Relying on evidence and following evidence.
[narrator] Since the letter led investigators
to the poison in Adam's car,
they take a deeper look at the bottle and receipt.
[Laurie] The receipt provides a lot of information,
and that Gmail account
now is something that law enforcement can look into.
[Mark] The Sheriff's Office was able
to get Adam Yoder's laptop and his cellphone.
A complete forensic examination
showed no evidence of the use
of the mradamyoder1990@gmail.com
e-mail address ever.
It was kind of our way of cleaning Adam Yoder very easily.
And now the person who's trying to put it on him becomes the sole focus.
[Tony] The absolutely critical next step in the investigation
is to understand when the account was created,
by what device, and when is it accessed and by what device.
[Mark] Whoever has control of that Gmail account
becomes very important to us
because whoever has control of that Gmail account
is the one that's purchasing this colchicine.
Gmail doesn't request any verification of the identity
of the person who sets it up.
So truly anyone, anywhere
can set up a Gmail account that says just about anything.
To further the investigation,
we need to know information that Google has.
[narrator] When investigators submit a subpoena to Google
requesting information on the account,
the company's response
provides them with a surprising new lead.
[phone ringing]
The response from Google shows that the account
was accessed from two different locations
using two separate IP addresses,
the house where Kaitlyn Conley lives
and the chiropractic office where Kaitlyn Conley works.
[Laurie] Every time it was always accessed
from the device exclusively used by Kaitlyn Conley.
That is a huge moment in this investigation.
Here is a person who is supposed to have been
a girlfriend of Adam Yoder,
a loyal employee of William and Mary Yoder.
So we call Kaitlyn Conley
and specifically requesting an interview with her.
As we're interviewing Kaitlyn,
we asked about what her status is with Adam.
She tells us she's no longer seeing Adam
or has not seen him or spoken with him
since September of 2015, about three months prior.
[Laurie] She describes how she felt like Adam mistreated her
a lot of times during the course of their relationship.
[Mark] Kaitlyn describes Adam as not a very hard worker,
he can't keep a job.
He's horrible with money.
[Laurie] Kaitlyn tells the investigators
when Adam found out that his mother was gravely ill,
first person that he reached out for was Kaitlyn Conley.
He told her he needed her
and asked her to please come to the hospital with him,
and at that point
they resumed a romantic relationship,
but an incident occurred
several months after Mary died,
in which Adam went back to the office
looking for evidence
of whom might've been responsible for his mother's death.
Kaitlyn and Adam got into a fight
and Adam was advised by his father to leave the office.
[narrator] But when investigators started asking Kaitlyn
about Mary's poisoning,
the interview takes a surprising turn.
Kaitlyn is asked if she knows what Mary Yoder died from
and she indicates that she doesn't know.
[Mark] I explained to her that Mary dies of colchicine intoxication.
And then she asked me how she spelled that,
so I took the corner of my notebook
and actually ripped out a page,
and I spelled out colchicine
and slid it across the desk to her.
[Laurie] But someone who assisted in taking over
Mary Yoder's practice advised Law enforcement
he had learned that Mary Yoder had died from colchicine toxicity,
and he shared that information
with Kaitlyn Conley in September.
So when she spoked to law enforcement in December
and denied knowing what killed Mary Yoder,
that was a lie.
[Mark] She's downplaying her knowledge of colchicine.
Why would a person care that they've ever heard of colchicine before
or why would they try to conceal that?
[Laurie] And at that point,
Mark Van Namee confronts Kaitlyn
as to the fact that this Gmail account
that's been accessed,
all roads point to her devices.
"We were back together and, you know,
he's been to my home.
He would have access to my computers,"
and attempting to point the finger at Adam.
[Mark] Once we start catching Kaitlyn in several lies,
obviously, that is very important.
We weren't catching Adam in lies,
we weren't catching William Yoder in lies,
and she keeps bringing up Adam.
Adam this, Adam this.
[Laurie] The investigator then decided,
"Wait a minute, we've got this anonymous letter"
pointing the finger at Adam Yoder,
we've got Kaitlyn Conley now
pointing the finger at Adam Yoder.
"Hey, maybe Kaitlyn Conley is the anonymous letter writer."
[narrator] If investigators can link Kaitlyn to both
the anonymous letter and the purchase of the poison,
they've found their killer.
But the question remains, why would she want to poison Mary Yoder?
[Lauri] Investigators were able to get a pretty good idea
of the type of relationship Kaitlyn and Adam had,
which quite frankly and ironically
was a toxic relationship.
Any time Adam Yoder broke off with Kaitlyn Conley,
she did something to bring him back to her.
She fabricated an ectopic pregnancy,
and he immediately came back to her.
She accused him of raping her
and being violent towards her.
Ironically, even after a rape allegation,
Adam Yoder went back to her,
and I think finally Adam realized
he just couldn't be with her anymore.
And when it ended finally,
Kaitlyn Conley decided she was going to do
one last thing to try to get him back,
and that was to kill his mother.
[narrator] Detectives are working a new theory
in the murder by poison of 60 year old Mary Yoder.
Could her officer manager, Kaitlyn Conley,
have killed Mary to punish her son, Adam,
for ending their relationship?
[Mark] Obviously, she has an extra grind with Adam Yoder.
They're no longer friends.
They had some sort of on-again, off-again relationship
throughout the years.
If you use the theory that the person that wrote the letter
was responsible for the homicide,
she becomes the main suspect.
[narrator] With the investigation shifting to Kaitlyn,
detective Van Namee gets another break
when the DNA analysis
of the two anonymous letters come back.
We've been notified that there's female DNA
under the stamp of the envelope.
So we ask Kaitlyn Conley to come in to give us
a fingerprint and DNA sample.
She not only comes to give her DNA,
but she brought the envelope from the office,
letterheads from the office.
Like, stuff that I did not ask for.
I mean, it was almost like she was going over the top to be helpful.
So I specifically asked Kaitlyn,
"Did you write to us the anonymous letter?"
And there was silence and she stated,
"You can't protect me."
Well, any answer another than a yes or a no
to a "yes, no" question,
you gotta ask the question again.
So I immediately asked,
"If you're the one that wrote us that letter I need to know,
you might be our only witness."
There was in that interview that Kaitlyn actually admitted
to writing the anonymous letter.
Kaitlyn makes the argument that she wants us to know the truth
in that she's scared of Adam Yoder.
[Laurie] I think at this point in Kaitlyn Conley's mind,
she is actually operating
in terms of self-preservation mode
and so her defense is to tell investigator Van Namee
that he wasn't a good boyfriend,
and that she was afraid of him.
He was physically abusive and hit her in the past,
and that's why she wrote the anonymous letter,
and that's why she didn't call the police
because she was afraid that he would come after her.
[Mark] Right after she admits to being the letter writer
and we are talking about Adam being a suspect,
and I'm going along with, you know,
"Why would Adam want to kill his mom," and this and that.
[Michael] Poisoning, at least, anecdotally
is a preferred method of murder
frequently among women because it is so insidious.
It does not require exertion of tremendous strength,
it does not involve a tremendous degree of violence.
It is a silent killer.
It's effortless effectively, which is what makes it so dangerous.
[narrator] Even with Kaitlyn's confession
to writing the anonymous letter,
investigators have no evidence that she poisoned Mary
and are forced to let her go.
[Laurie] It's frustrating that you have somebody sitting before you
who you know has probably in a very cold and calculating manner
cause the death of someone who was very well loved in the community.
It's frustrating to know that you have to let them walk out the door.
You don't have enough evidence at this point
to maybe arrest them.
[narrator] As investigators continue building their case against Kaitlyn,
they get a surprise visit from Adam Yoder.
[Laurie] He told investigators
that in his relationship with Kaitlyn Conley,
he had gotten very ill almost three months
to the day prior to his mother getting very ill.
He had been given Alpha Brain pills
by Kaitlyn Conley and he had become very ill.
So he sort of half joking asked her
if she had poisoned him.
That actually caused a fight between the two of them,
but it was something that had always been in the back of his mind.
It is our belief that Kaitlyn Conley
caused Adam Yoder to ingest colchicine as well.
[narrator] With a potential pattern of poisoning stablished for Kaitlyn,
detectives dig into the details
of the colchicine purchase.
[Lurie] Investigators learn prepaid credit cards
were used to purchase the colchicine
and they were able to trace them back
to being purchased at a local grocery store.
[Mark] They had no other purchases on those credit cards,
so it became very important to us,
whoever purchased those credit cards
that were used for the colchicine,
they had one mission,
they were trying to buy a poison.
[narrator] Investigators called Kaitlyn back in,
hoping they can bluff her
into admitting she purchased the credit cards
used to buy the poison that killed Mary.
[Mark] In an investigation when you're in a room
with somebody, you can use a prop.
The decision was made that we would tell her
we had security video
of that purchase from the supermarket.
She continually said, "That's not me.
Adam must've done it. Not me, not me, not me."
[Mark] She could've said, "I didn't buy them."
But no, she believed at that moment I had her.
[Laurie] It was a risk at that point we felt like we had to take
because we wanted some admissions from her.
[Mark] We proved that Kaitlyn was the one that bought the credit card.
She's the one that has control of the Gmail account.
I mean, we can put the poison in her hand,
we can't do that with anybody else.
There's no doubt she's the one that's responsible for Mary Yoder's death.
One has to wonder if a part of the motive in this case was somehow to punishing Adam.
That having him suffer through this death
and effectively claim two victims in the process.
[narrator] With Kaitlyn's confession to purchasing colchicine,
detectives are now able to reconstruct Mary Yoder's final hours.
[Mark] Kaitlyn arrives at the office on July 20th,
just prior to 8:00 a.m.,
Mary arrives approximately at 8:30 a.m. to begin her day.
Mary leaves the office approximately at 12:30 p.m.
to go have lunch with her mother.
[Laurie] It would've been during the lunch time
where Mary Yoder was out of the office
and Kaitlyn Conley was alone there by herself
that colchicine was placed in the protein powder shake
that Mary Yoder drank around 1:30 that afternoon.
Kaitlyn Conley remained in the office with Mary Yoder
until around 6:30 that evening of July 20th.
Forty-eight hours after ingesting the colchicine,
Mary Yoder died from colchicine toxicity.
[narrator] Detectives arrest Kaitlyn Conley
and charge her with second degree murder.
At trial, she gets eventually convicted
of the lesser charge of first degree manslaughter
and is sentenced to 23 years in prison.
Kaitlyn Conley thought a long time about this.
She spent a lot of time planning this.
Based on everything I observed,
I would describe Kaitlyn Conley as a cold,
calculating sociopath.
There's no doubt about it, it was almost the perfect crime.
She came very close to pulling it off.
[Tony] One of the things I think about often
is how easily this case could've never been solved.
Justice for Mary Yoder
very easily could've been lost.
She loved her family very much, she loved her job.
She loved her practice, she loved her patience.
She was just incredibly passionate
about helping people and doing what was right.
Clearly, she was lost long before she should've been.