00:00:00
[THEME MUSIC] NANCY GRACE: May 1988, Santee,
California, a small city just East of San Diego.
00:00:19
Local police get a
distressing call. A young mom has
been found savagely murdered in her own home.
00:00:28
She did not show up to work,
so a co-worker went to her house to find out why she wasn't
answering her phone or showing
00:00:34
up to work and discovered
that the door was open, and then he discovered
Diane in her bedroom.
00:00:40
NANCY GRACE: The
victim is Diane Dahn, the mother of a two-year-old
little boy Mark.
00:00:46
Police find Mark wandering
around the house, his mother's blood is on
the toddler's clothes.
00:00:56
There's a certain
amount of questions that come along with that, you know. Like, why-- why didn't I die?
00:01:02
NANCY GRACE: The leads
come and they go, and then the leads end. But then, 30 years later, a
groundbreaking new forensic
00:01:12
tool blows this case wide open. You can take a case
that's 30 years old and solve it with what you did.
00:01:21
With all of the
new technology, you can't get away with it anymore. This is the story
of a horrible murder
00:01:29
of a young mother. Her tot son, who was
there when she died, and his 30 year quest to
know what happened to my mom.
00:01:41
I'm Nancy Grace. Welcome to "Bloodline
Detectives." [THEME MUSIC] NANCY GRACE: Santee, California,
May 1988, a small city
00:02:13
in Southern California. It's a pretty small town. It's grown obviously
over the years.
00:02:20
Back in the 1980s, it was
probably a little sleepier than it is now. It's been built up a lot.
00:02:25
It had a reputation
as being, you know, people who are
generally very independent
00:02:31
and very different
than perhaps the folks who lived on the coast. NANCY GRACE: One of these
free-spirited residents
00:02:37
is 29-year-old single
mom Diane Dahn. Diane Dahn was a
single mom raising her two-year-old son Mark.
00:02:46
They lived in an apartment
complex in Santee off Graves Avenue. She worked for the
transportation company
00:02:54
here in San Diego. She was a musician. She was a violin player
and lots of people
00:03:00
knew her as a really
good musician. She was kind of a fun-loving,
free-spirited hippie,
00:03:07
I guess is the way she's
been described to me, which is interesting. Because then they always say,
oh you're a lot like her.
00:03:12
And I think, well,
yeah, I guess-- I guess I kind of am like that. These are happy, carefree
times for a young, single mom
00:03:20
and her toddler son. Then, on May 2, 1988, Diane
doesn't show up for work. Her coworker, Gary Beyer, goes
to her home to see if she's OK.
00:03:34
So a coworker
went to her house to find out why she
wasn't answering her phone or showing up to work and
discovered the door was open.
00:03:42
Mark was kind of walking
around, not being watched, and then he discovered
Diane in her bedroom.
00:03:52
911 OPERATOR (ON
PHONE): 911 emergency? GARY BEYER (ON PHONE): A
lady laying on the ground.
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She's dead. 911 OPERATOR (ON PHONE): OK. Where are you, sir? GARY BEYER (ON PHONE): I'm
trying to think of the street.
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911 OPERATOR (ON PHONE): OK.
Are you on Graves Avenue? GARY BEYER (ON PHONE): Yeah.
00:04:02
911 OPERATOR (ON
PHONE): Let me get you the fire department, OK? GARY BEYER (ON PHONE): OK.
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911 OPERATOR (ON PHONE): OK. FIREMAN (ON PHONE): Hello. GARY BEYER (ON PHONE): Hello.
00:04:09
This is Gary Beyer. FIREMAN (ON PHONE):
What's the problem? GARY BEYER (ON PHONE): There's
a dead body in the bedroom.
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FIREMAN (ON PHONE): Is
that where you live? GARY BEYER (ON PHONE):
That's where she lives.
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FIREMAN (ON PHONE):
Where is she? What's the address? GARY BEYER (ON PHONE):
It's on Graves there.
00:04:20
It's an apartment. FIREMAN (ON PHONE): Are
you calling from there? GARY BEYER (ON PHONE): Yes.
00:04:23
FIREMAN (ON PHONE): OK. 729. Do you know how she died?
GARY BEYER (ON PHONE): No.
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I sure don't. They missed her at
work, and I came over to see if she was
sick, and I just
00:04:32
seen her laying on the ground. FIREMAN (ON PHONE): Gary,
we'll be right there. GARY BEYER (ON
PHONE): Thank you.
00:04:36
I have no recollection
of any of that, but, yeah, I guess,
I had blood on me, so I don't know if I was
close to the situation.
00:04:45
You know, there's a certain-- there's a certain
amount of questions that come along with that, you know.
00:04:49
Like, why-- why didn't I die? We have jurisdiction over
that part of the county,
00:04:56
so they would have called us. Then a deputy would have
been the initial responder
00:05:01
to examine the scene,
you know, kind of figure out what's going on. Given the crime, given
that Diane's body was found
00:05:10
in the bedroom, then
the homicide unit would have been called to the scene. BRIAN PATTERSON: Sheriff's
Department came out,
00:05:16
determined she was deceased. It was quite obvious it was
probably a homicide based
00:05:20
on what they saw, so
they secured the scene and called the homicide detail. She had sharp force object
injuries to her body.
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It appeared she had
been beaten a little bit or some on the face and head. Imagine the dilemma
detectives now face.
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Is there a way to
coax young Mark to tell them what he has seen
without adding to his trauma?
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He gave some description
as a two-year-old might give, but some description of a man
that had been in the apartment.
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We don't know if he actually
witnessed the attack. I don't believe he gave any
indication that he witnessed
00:06:01
something bad happening
to his mother, but he definitely gave some
information about the man.
00:06:07
When they talked to Mark,
he was young obviously, and if I recall correctly,
he said a bad man hurt Mommy.
00:06:14
But tot boy Mark
cannot recall very much, so police begin to retrace Diane
Dahn's last known movements.
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They discover that Diane and
Mark had dinner the night before with
co-worker Gary Beyer,
00:06:29
the friend who discovers
her body the next day, and his wife Marilyn. This couple will now
play a remarkable role
00:06:38
in this tragic story. The family decided who
would be best to raise Mark and the Beyers,
the family that she
00:06:47
had dinner with
the previous night and friends of the family,
ended up raising Mark.
00:06:53
So the Beyers are
my adopted family. My mom and dad. They worked together,
her and Gary,
00:07:00
and I guess when
all this happened, they just felt
compelled to take me in, and I never knew the difference.
00:07:10
I was loved. I had a good life. I had all the things that
a normal child would have,
00:07:14
you know. I fell on my bike, busted
my head, all that stuff. So they were very good to
me, and now that I'm older,
00:07:22
I can look back and
think how fortunate I was to have that in my life. NANCY GRACE: Fortunately, little
Mark is secure with Marilyn
00:07:32
and Gary Beyer. Meanwhile, investigators
are struggling. They have a picture of how Diane
Dahn is murdered, but no clue
00:07:42
as to who killed her. Any victim of a
crime, I imagine there was absolute terror.
00:07:48
We don't know what happened
prior to the murder. Was this somebody that she knew?
00:07:54
Knew well? Had just met? A complete stranger? Whatever the situation, whatever
the relationship between her
00:08:00
and the suspect, I can't
imagine that it would be anything but just terror. The realization that this is
taking a very violent turn.
00:08:09
Plus she has a kid. She's in this apartment
with a young child that she's caring for.
00:08:14
And by all accounts, talking
to family members decades later, loved her son very much.
00:08:20
And I would imagine
that's the other thing that goes through your mind. I need to protect my child.
00:08:26
A toddler tells police that
a, quote, bad man hurt Mommy. But who is this
so-called bad man?
00:08:35
A vicious killer that
took his mother's life. That's next on
"Bloodline Detectives."
00:08:49
NANCY GRACE: Santee,
California, May 1988, police investigating the murder
of 29-year-old young mom Diane
00:08:58
Dahn. Her two-year-old son Mark
found at the crime scene covered in blood,
his mother's blood,
00:09:06
and wandering around
the apartment. Little Mark cannot remember
very much of what he saw.
00:09:13
Police focus instead
on the crime scene. This seemed to be an attack
that happened very quickly
00:09:22
and not thought out and planned. That it ended up
having, you know, a fair amount of evidence left
behind for the investigators
00:09:29
to go through. The detectives arrived,
they collected fingerprints inside the apartment.
00:09:36
I believe they collected some
clothing that belonged to her, a pillow that was out of place.
00:09:40
There was DNA evidence
obtained at the time. DNA really wasn't out
there at that time in 1988,
00:09:47
but they did collect
fingernail scrapings, hair. NANCY GRACE: Investigators
struggled to determine
00:09:54
the motive behind the murder. There was no evidence
of sexual assault. She was nude, which you
could assume, I guess,
00:10:03
that there is some
kind of sexual nature in maybe the attack. But as far as
actual evidence, no.
00:10:09
She did have what
would we would probably consider defensive wounds
based on fingernail scrapings.
00:10:15
There was DNA under her
fingernails that were male DNA. Hair that was in her hand.
00:10:20
So it did look like
she put up a fight. The original
investigators obviously spent a lot of time taking
a look at that evidence,
00:10:28
but we're talking
1988, and the use of DNA as part of
an investigation was in its infancy.
00:10:38
They did discover that it
was not the same hairs that belonged to Diane herself, but
they were never able to connect
00:10:46
it to a possible suspect. In 1988, no, I don't think DNA
would have been on their minds.
00:10:52
They have foresight to
know to collect things and to keep it for
possible future analysis.
00:11:01
They would be put into
evidence in the Sheriff's property and evidence
room, and they
00:11:05
would be stored under that case
number in our evidence lockers. Yes, the autopsy was performed
and a cause and manner was
00:11:14
homicide by sharp force injury. NANCY GRACE: The crime scene
evidence is safely secured
00:11:19
and the results of the
autopsy made available. Next up for investigators, a
list of potential suspects.
00:11:28
You have no suspect. You have some cases
where the suspect might be sitting on the
porch waiting for an arrest.
00:11:36
But in this case, there
was no obvious suspect. She lived in an
apartment complex,
00:11:41
so they would have canvassed
the complex for any information regarding people
who knew her, people
00:11:47
who potentially
dated her, you know, just people who were
in her life somehow. The original detectives looked
at kind of the usual suspects,
00:11:57
boyfriends, friends,
people that she might have known, because
it didn't look like there was a forced entry.
00:12:02
So possibly somebody she knew. They would have
poked a little bit deeper to see is there somebody
there who was angry at her?
00:12:10
A grudge. Had she dated somebody
that she broke up with? So we would have had to go
on into her private life
00:12:17
as much as possible. This is a very special case,
even for veteran detectives. As the investigation stalls
and time begins to pass,
00:12:27
police never forget
about Diane's son Mark, and they check in on
him regularly to see how
00:12:35
he's coping without his mom. But they also hope
that somehow he might remember just
something from the day
00:12:43
his mother was murdered. I remember sitting down
with a psychologist that came and talked to me
to see how I was doing,
00:12:51
and the police a
couple of times. But throughout the
years, I remember them coming over and asking
questions and things.
00:12:59
But as the case gets colder,
I think it just kind of, you know, they're not going
to get any more information,
00:13:04
so it just kind of ended. People have to get
on with their lives, and even though this leaves a
big hole because a loved one is
00:13:14
killed and they have no answers
other than the fact that they were killed, people go on.
00:13:20
And I think it's not
that they gave up. I don't know if
you ever give up, but there's a certain
acceptance after 30
00:13:27
plus years of no answers
that this is just the reality that you have to deal with.
00:13:33
NANCY GRACE: As
Mark grows up, he struggles for answers
to a loss that baffles everyone, including the police.
00:13:41
As the years went by, I think
it was probably my early teens when I really started
questioning, well,
00:13:49
why did this happen? How did this happen? Who did it? All those kind of questions
that would typically
00:13:54
pop up in anything like that. That's when I started
thinking to myself, you know, what
would life have been
00:14:00
like with somebody that was,
from what I'm being told, is just like me? You know, what would it be like
to be loved by your own mom?
00:14:15
NANCY GRACE: Mark desperately
holds on to anything that physically connects
him with his mom.
00:14:21
I started gathering
what I could from my grandmother and
pictures of her, which I still
00:14:29
have a pretty good collection. I had some notes of hers
from marine biology. So living so close
to the ocean, I
00:14:36
got really, really into
a lot of the creatures that are in the ocean. And then I would go back and
I would refer to her notes
00:14:44
and say, OK, look, she had
a note in there of this. So there was kind of always
an interesting connection.
00:14:51
I think I took a lot
of solace in the fact that her body was cremated
and thrown into the ocean.
00:14:57
So still to this day,
when I go to the beach here in Oregon, even though
it's nowhere near San Diego,
00:15:04
I feel connected. I feel close. And it's almost as if you
can just feel her presence.
00:15:12
NANCY GRACE: The murderer of
a young single mom Diane Dahn remains cold, nearly 20 years.
00:15:18
But then, 2006, the
San Diego Sheriff's revisit the case thanks to
a brand new DNA technology.
00:15:28
One investigator,
Victor Caloca was the investigator
in the early 2000s who picked up this
case, and this usually
00:15:36
happens with cold cases. This murder happened
in 1988, and there would have been a group of
detectives who worked on that.
00:15:44
And then, it went cold,
and then eventually transfers, retirements, it gets
passed on to another detective.
00:15:53
And so Victor was
probably in a line of detectives whose
fingers touched this case at some point.
00:16:00
Victor put in a lot
of work to this case and advanced it
as best he could, but again, even
in 2006 and 2007,
00:16:08
where he did a lot of work,
the DNA had not yet advanced and IGG certainly had not become
a part of our investigations
00:16:18
as we know it has in
the last few years. Criminologist Cathy
Chang then makes a remarkable breakthrough.
00:16:28
She searches through tiny
pieces of evidence found in the victim's hand
and she identifies
00:16:35
a DNA sample from a hair. She, Chang, believes it
may belong to the killer. What I would do first is I
would look at the evidence,
00:16:49
and in this case, there
was a lot of hairs. And hairs are actually
really difficult to get
00:16:54
a DNA profile from. If you have a hair that
is actually pulled out from somebody's head or wherever
that hair is coming from,
00:17:03
and the root is still in the
active growth phase, what happens is when the
hair gets pulled out,
00:17:10
there's still tissue that's
attached that's a really good source of DNA. So it was my role to go
through the hairs in this case
00:17:18
and there were hundreds of them. I went through more than
200 hairs, in this case,
00:17:25
and was able to identify a
handful for DNA analysis. Most of the hairs that
I did DNA analysis on
00:17:35
came back to the
victim in this case, but there was one hair that had
a profile from an unknown male.
00:17:41
It didn't match any of the
other reference samples from other potential suspects
that were in the case.
00:17:48
And so what I do is I write my
report, say there's a profile, it doesn't match the victim.
00:17:54
It doesn't match any of
these other individuals. And then the profile
was entered into CODIS.
00:18:00
NANCY GRACE: Police working on
Diane Dahn's case submitted DNA sample from the suspected
killer into CODIS,
00:18:07
the national database
of DNA profiles from convicted offenders. So the DNA that was identified
was a partial profile that
00:18:17
was suitable for CODIS entry,
and it was put into CODIS, and there was never a hit.
00:18:23
The problem with
the CODIS database is whilst it has 20
million people in it, the overwhelming crime, doesn't
matter where in the world,
00:18:32
is generally committed by males
between the age of 15 and 35. The CODIS database was
started back in the mid 90s.
00:18:40
It's aging out. In other words,
those people that are in the database the
longest, they're not
00:18:46
going to be committing crime. They may have died. So they've become less useful.
00:18:51
So even though it has 20
million people, it's aging off, so it's going to
become potentially
00:18:55
less relevant over time. After exhausting all leads
and all the potential suspects,
00:19:02
and once DNA came about and
they were able to eliminate all the people that they
thought were suspects,
00:19:09
there was no other evidence. Ultimately, once everything
has been exhausted, all the leads, all the
evidence has been processed,
00:19:17
it goes cold and goes
into the archives. It's a kind of a misnomer. When people say it's cold,
people kind of think that we
00:19:26
don't ever look at it again. That's not true. It's cold in the
sense that there is not an active
daily investigation
00:19:35
barring new leads. But if there are new leads, then
that becomes a warm case again.
00:19:40
And at any point,
these cold cases can get reviewed
given new evidence, and that's what's very
exciting about investigative
00:19:49
genetic genealogy. It gives us the opportunity
to kind of reclaim these cold cases and
resolve them in a way
00:19:58
that we probably
couldn't have before. Can investigative genetic
genealogy ID Diane Dahn's
00:20:07
killer? We find out next on
"Bloodline Detectives." [THEME MUSIC] NANCY GRACE: It's now over
20 years since the 1988
00:20:23
murder of 29-year-old single mom
Diane Dahn, Santee, California. The case remains
cold until detectives
00:20:33
turn to a new forensic
science, investigative genetic genealogy. So genetic genealogy is
when you have a DNA profile
00:20:44
and you want to identify
relatives of that DNA profile. And it started decades ago
with people who were adoptees,
00:20:53
and they wanted to know
who their biological family members were. In 2018, the Golden State
Killer was identified
00:21:00
through genetic genealogy
and that kind of opened the floodgates to use
it for case investigations.
00:21:08
So myself and others
in the homicide unit attended a briefing given by
the FBI and people who worked
00:21:17
on the Golden State Killer
case, where we were introduced to this way of solving cases
that seemed unsolvable,
00:21:26
as long as you have
the presence of DNA. The way it's used in
terms of a criminal case
00:21:33
is you have a DNA
profile that's unknown and you want to know
who are the family
00:21:40
members of this individual. And by creating
those family trees, getting those connections,
you can potentially
00:21:46
identify that unknown person. The science of investigative
genetic genealogy is really expensive and it calls
for great scientific expertise.
00:21:58
Normally, police departments
outsource this research to professional labs, but the
San Diego Sheriff's Department
00:22:07
tries a different approach. They want to learn these
techniques for themselves and train their
detectives to use
00:22:15
investigative genetic genealogy. So 2019, we kind of had either
the arrogance or the chutzpah,
00:22:27
the naivete to
decide that we were going to do this on our own. A lot of law enforcement
agencies are using IGG.
00:22:36
Almost all of them farm out
the genealogy part of it. We decided that it might
be beneficial for us
00:22:43
if we could learn
to do the genealogy. We go to a commercial
company, they're going to build out this whole
tree and take as much time
00:22:50
as it takes, and we're
going to pay for that. Where I have my detectives
and my analysts doing it,
00:22:55
let's say we have a high match. We have a third or fourth
cousin to our person that we're looking for, either
our victim or our suspect.
00:23:01
Well, through law
enforcement databases, we can start looking at
the people in that tree
00:23:04
and see who has
ties to San Diego. So if we're looking
at a case and we get a low match to say a
third or fourth cousin,
00:23:12
and they're on the East Coast. And we start looking at
that whole family tree and everyone's on the East
Coast except cousin Bob, who
00:23:18
was in San Diego for four
years in the Navy, well, we can jump straight to cousin
Bob and start looking at him.
00:23:25
And see if he was in
the area at the time, if any ties to our victim. So it actually
saves a lot of time.
00:23:31
The team at San Diego
Sheriff's Department begins the process of building
the suspect's family tree.
00:23:39
They have a DNA sample
retrieved from the crime scene. However, it does not
match any known offenders.
00:23:49
Investigators now need to
put the DNA sample in more databases besides CODIS. So IGG becomes appropriate
when you have the presence
00:24:01
of DNA, you have had no
hits in the CODIS database, and you have the potential
to have a private lab examine
00:24:11
your DNA, process it so that
it's in a form that could be read by the
genealogical databases
00:24:19
that we're allowed to use. And then the last hurdle
that they have to meet is is there enough extracted
DNA left that we can send
00:24:28
it out for genetic genealogy? When I go from quant
to amplification, sometimes when I do that
step, I consume my sample.
00:24:40
I use all of the DNA that I
have to try to get a profile. In this particular
case, I had enough DNA
00:24:48
to attempt to get a
profile, and there was still enough DNA left over. And so we were able to take
that remaining extracted DNA
00:24:55
and send it off for
genetic genealogy. We had a private lab
do the SNP analysis.
00:25:03
Single nucleotide
polymorphisms, SNPs. We share 99.7% of our DNA. That 0.3%, in a
very general sense,
00:25:13
is it causes the
difference between us. How you look, the
color of your hair, the blue eyes, all of those
things are because of SNPs.
00:25:21
They give us our diversity. So we take advantage of
that diversity to help now say how much DNA do you
share with someone else?
00:25:30
You can look anywhere
between 10,000, which is what
Berrigan developed, 10,000 SNPs, all the way up
to 600,000, 700,000 SNPs.
00:25:40
You then upload that
profile to GEDmatch. NANCY GRACE: GEDmatch
is a California based
00:25:46
company that compares DNA data
files from different testing companies. What's particularly unique
about GEDmatch is that they
00:25:57
allow people or
profiles from all the major genealogical
companies to-- you can upload their kits and
then match against everybody
00:26:07
else in their system. That's unique because if
you do an Ancestry kit, you're only going to
match against people
00:26:13
who have done another
Ancestry kit in that world. But if you move an
Ancestry kit to GEDmatch,
00:26:18
you can potentially
match against somebody who did a 23 & Me or
MyHeritage or Family Tree DNA.
00:26:26
NANCY GRACE: By 2020, the SNP
analysis on the DNA sample is complete. Now the newly trained
genealogist at San Diego
00:26:34
Sheriff's attempt
to create a family tree using the refined DNA
sample as a starting point.
00:26:44
We were fortunate that
our initial high match, and what that means, whenever
you're looking at how somebody
00:26:50
is related to somebody
else, the shorthand that we use in genealogy
is centimorgans,
00:26:55
which is basically just
the genetic distance between two people. If you have a high
centimorgan match that means
00:27:03
you're closer in relation
than you are if you have a low centimorgan match. In Diane Dahn's
case, we are fairly
00:27:10
fortunate in that our highest
initial match was almost 200 centimorgans, so that would
have indicated probably
00:27:17
a second cousin relationship. That's exciting
because when you have that close of a
relationship, you're
00:27:23
not going to have to necessarily
go back 7, 8, 9 generations before you can move forward.
00:27:27
The next thing
that we have to do is build trees, family trees. We have this known
person, we have to start
00:27:33
building that family tree. We got very excited
because this family among whom this match was
from had a lot of connections
00:27:44
to San Diego. One of the benefits of
doing all this in house is that we can consider
things like geography and time
00:27:53
and people who are
already in the case file. And obviously, this
wider family had
00:27:59
a few known felons in the group,
had deep San Diego connections. Who in the end, had absolutely
nothing to do with the homicide
00:28:09
other than that
they were related ultimately to the person
who was responsible. It is painstaking work.
00:28:20
The team follows
genetic lines, which, one by one, lead to dead ends. This is, in fact, progress
because it's really
00:28:31
a process of elimination. Detectives know
that each failure brings them one step
closer to identifying
00:28:40
the correct genetic line. We worked a different
side of the tree and that's where we
discovered another group
00:28:51
of folks that also had a
relationship to San Diego. But more specifically,
a couple of people
00:29:00
had a relationship to Santee,
and that became kind of key to us unlocking the
identity of this case.
00:29:13
NANCY GRACE: Eventually,
the Bloodline Detectives make a breakthrough. They identify a
name, a man linked
00:29:20
to Santee, who
detectives believe may be related to
Diane Dahn's killer. He was related, funnily
enough, to the high match
00:29:31
clearly, because this
person was a high match, and I believe he ended up
being a second cousin, which
00:29:37
confirmed for us kind
of the initial work that we had done
trying to figure out how is the high match
related to this unknown person?
00:29:46
The suspect that we identified
was Warren Robertson. NANCY GRACE: So who is Warren
Robertson and where is he now?
00:29:54
We find out next on
"Bloodline Detectives." [THEME MUSIC] NANCY GRACE: It's now 30
years since the brutal murder
00:30:11
of young mom Diane Dahn
in Santee, California. Her brutalized body
discovered in her apartment
00:30:19
while her two-year-old son Mark
is there found wandering around covered in his mother's blood.
00:30:27
Now, new DNA technology
gives genealogists at the San Diego Sheriff's
the name of a prime suspect,
00:30:35
Warren Robertson. We had a suspicion
that Warren, just based on
information that we
00:30:44
were able to gather about
where he lived in the 80s and where he was
in the family tree,
00:30:51
that this was somebody that we
should look into more clearly. As we eliminated other
people, at some point,
00:30:59
we were only left with
Warren as a possible suspect. But that's not
proof just thinking
00:31:05
that it had to have been him. You have to go out somehow
and connect him genetically
00:31:13
to the DNA left at the scene. As police attempt to connect
Robertson to the murderer,
00:31:20
they inform Diane
Dahn's son Mark of the latest breakthrough. Mark doesn't
remember his mother's
00:31:26
murder despite having been
in the apartment the night she's killed. I was on my way to the
coast, of all places,
00:31:35
and while driving, I got a text
message, and I gave him a call. And he kind of gave me a
brief description of what was
00:31:43
going on, and I was in shock. And, you know, that's when all
the anxiety and the excitement
00:31:49
kind of kicked in. What's going on? What did they find? How did they even do anything?
00:31:53
Why did it take so long? A lot of questions popped up. But then I was able to
have a video call with him,
00:31:58
and he explained things
further about the genealogy and how they were going
through people's trashes
00:32:04
and collecting DNA samples. And I thought, my god,
you've got to be kidding me? Like, all of that
stuff is now possible
00:32:11
and it just blew my mind. It really blew my mind. NANCY GRACE: The
Bloodline Detectives
00:32:16
need to connect the DNA
sample from the crime scene with Warren Robertson's DNA.
00:32:23
As they close in on
Robertson, investigators dig deep into his lifestyle. Warren was born in Arkansas.
00:32:31
He came out here. He was living here. He met his wife. He had a son. He was into drugs.
00:32:38
He was using drugs. His wife ultimately
left him with their son, and then he had been
arrested several times
00:32:46
for some petty drug
stuff, property crimes. It appears that he lived in
the same apartment complex
00:32:52
as Diane did at the time. We spoke to relatives of
Warren that also lived there,
00:32:57
and they confirmed
that they all lived there in that same complex. And he lived in a
building just off of hers
00:33:04
where he could see her. He had moved out of the area
at some point after the murder,
00:33:11
but not right after the murder. Had moved to the Midwest. As is the case with
many older cases,
00:33:19
Warren Robertson had died
in a house fire in 1999. NANCY GRACE: Warren Robertson's
death in a house fire
00:33:27
means that Diane Dahn's likely
killer has evaded justice. It's a setback. That's true.
00:33:34
But it's not the end
of this investigation. We identified the
suspect's children.
00:33:41
We had identified his
ex-wife and the wife he was married to when he died,
and we picked up the phone
00:33:50
and called his son and told
him this extraordinary story. But we weren't just
interested in telling a story.
00:33:57
We were interested
in getting his DNA. Because if we could get
his DNA, and we could match
00:34:04
it to suspect DNA, then
we knew that we had arrived at the right person. In the son's case, and in others
that we talked to about him,
00:34:14
they were happy to help. He really didn't have a
relationship with his father, and he, like most people
that we talked to,
00:34:23
wanted to know the truth. He said, I don't want
to think of my father as somebody who killed
somebody, but if he did,
00:34:31
I don't want to stand in the way
of having that fact come out. So he agreed to
cooperate and help us.
00:34:39
What the detectives had
to do was to get DNA samples from family members
of the individual,
00:34:45
and then I would do a
type of paternity analysis that involves his child
and the child's mother
00:34:53
and see if whoever is the
owner of the DNA on that hair, could that individual be
the father of this profile
00:35:05
that I obtained from a
particular individual? So it's a paternity
analysis is what we call it.
00:35:11
A vicious murder is so
close to being solved. Will a son, now a man,
soon have more answers
00:35:20
than questions about what
happened to his mother? That's next on
"Bloodline Detectives."
00:35:27
[THEME MUSIC] NANCY GRACE: San
Diego, California. After over 30 years, thousands
of hours of police work,
00:35:41
detectives finally get the news
that they've waited so long to hear, the identity
of the man who
00:35:48
murdered young mom Diane Dahn. He supplied his DNA and they
examined it in the crime lab.
00:35:54
Even though they
don't do SNP analysis, they can do Y-STR analysis,
where they can see that there
00:36:01
is an extraordinarily
high probability that the DNA of the son is
related to this unknown DNA.
00:36:08
And that was true, leading
us to target Warren Robertson as the suspect and as
the person responsible
00:36:17
for the murder of Diane Dahn. NANCY GRACE: One
of the first people detectives inform
of the breakthrough
00:36:22
is Mark, Diane's son. It was just a text message,
and I thought to myself, OK, that's interesting.
00:36:32
And then I got a
look at the guy. He had sent me from previous
times this is who he suspected,
00:36:38
so I had a picture of him. And then later on, we had
a conversation on the phone
00:36:43
about who he was and why he
did what he did hypothetically, or a theory as to why
he did what he did.
00:36:51
And it turns out he was just
kind of a guy who was probably on drugs and just kind
of went on a spree
00:36:58
going through the apartments
and she was collateral damage. It brings closure, I guess.
00:37:06
In a weird way, it was
more like that makes sense, rather than having
question after question
00:37:11
as to why this was there. Why did this happen? It was more, that makes sense. It's not right, but at least I
have answers to the questions
00:37:20
that I've had for so long. NANCY GRACE: San
Diego Sheriff's go public with the news this cold
case has finally been solved.
00:37:28
At an emotionally
charged news conference, Diane's sister Victoria
says she never gave up
00:37:36
hope that this day
would eventually come. I'm so grateful to the
detectives and everything
00:37:44
that has been done. I didn't think anything was
ever going to come of this. The detectives have done
such a wonderful job.
00:37:52
I can't even begin to
give them enough praise. Detective Patterson
was persistent,
00:37:58
and when he came back and
said that they got a hit, it probably was, other than
the birth of my children,
00:38:07
the best day of my life. NANCY GRACE:
Investigators reflect on lessons they learned.
00:38:13
They believe that
training their staff to utilize investigative
genetic genealogy techniques
00:38:19
is a game changer. The San Diego Sheriff's
Department, we're very lucky. Is we have a large department
with a very good budget,
00:38:28
but we don't have a huge
crime rate like Chicago or LA or New York, so we
have time to work
00:38:35
our cases very, very in-depth. Not to say that they
don't, but we're able to put four detectives
focusing on this type of stuff.
00:38:42
And I still have enough
detectives to do work in all the other current homicides.
00:38:45
You have to have the
resources and the and the financial ability to do it. And then having
your own crime lab,
00:38:50
we're able to cut
down a lot of cost too instead of having
to farm everything out.
00:38:54
We've been working
this four years, and I think up to this point,
we have resolved nine cases,
00:39:00
and we are actively working
a half a dozen more. And there are a lot of other
cases that are in line.
00:39:08
We're very to moderately
close on four other cases, and we hope to be
able to make more
00:39:15
announcements in the future. Now that we're comfortable as
investigators, as analysts,
00:39:19
as we sort of deepen our
knowledge and our training about genealogy,
we will get you.
00:39:25
Maybe not today, maybe not
tomorrow, but we will get you. Investigative
genetic genealogy
00:39:32
is a game changer thanks to the
increasing number of people who test their own genetic makeup.
00:39:40
The results of these
tests in large databases can help law enforcement crack
seemingly uncrackable cases.
00:39:51
If I look back
at my life, as much as I would have loved to
have spent time with her,
00:39:57
everything happens for a reason. And when I say that, I mean,
because of the things that have
00:40:02
happened to me, that's what made
me who I am today, who I feel is a pretty good person.
00:40:11
And without those things, maybe
it would have been better, maybe it would have
been worse, but I
00:40:17
am who I am today because
of all of the things that have happened to me. No matter how big of a trauma
it seems in the moment,
00:40:25
it's going to make you
into something great if you allow it. What's so remarkable about
investigative genetic genealogy
00:40:37
is that criminals who think
they've gotten away with murder now find there is no
hiding from science
00:40:45
and their own family's DNA. The next knock on their door may
be Lady Justice serving it up,
00:40:55
even after 30 years. I'm Nancy Grace. Thank you for being with us
here on "Bloodline Detectives."
00:41:03
[THEME MUSIC]