One Deadly Mistake

a brutal crime scene.

- Her body was lying on the floor

in a pool of blood.

- We can see blood on the pillows.

There's blood on the bed.

- and the only way I could process it was...

Disbelief.

- nine days later, two more victims.

- They were found in their bed after their murder.

- The crime scene photos were horrible.

- A neighbor with a shocking piece of evidence.

- This guy is outside with a video camera.

- I watched that video thousands of times.

Whoa, who's car is this?

- detectives finally hone in on a killer's crucial mistake.

- without it, police may never have been on his trail.

- we didn't have a lot of time.

- I told him that you're the one who killed them.

- I get goose bumps thinking about that verdict.

austin, texas...

The booming state capital is known for its sleek skyline

and its laid-back sensibility.

but late one chilly December afternoon in 2014,

the city's usually peace is broken by a disturbing call.

- the 911 call was from the victim's son

who reported that he had come home

and found his mother deceased.

One of the supervisors from the homicide unit called me,

gave me a brief description of what was going on,

told me where to go, and I drove out to the scene.

- the normally quiet neighborhood

is buzzing with police activity.

Once I got on scene,

I met with the officers who were already there,

and they did a very good job of making sure

that we had a pretty pristine scene when we went in.

- The house belongs to kathy blair,

a 53-year-old high-school music teacher.

In the bedroom, detectives encounter

a bloody and disturbing scene.

- There's blood on the pillows.

There's blood on the bed.

Kathy blair is located on the floor.

There were stab wounds in her chest and in her neck.

Based on the scene,

my theory was that she had been asleep on the bed

when she was attacked.

It was very clear based on the patterns

we saw in the blood that...

She was fighting for her life.

- not far from the bed, there's another disturbance.

- There's a full-sized jewelry box.

It's a piece of furniture that sits by itself.

All the drawers from that had been removed...

So, presumably, the jewelry had been taken.

- Investigators look through the rest of the house,

but despite the ransacked jewelry box,

this doesn't seem to be a burglary gone wrong.

- The problem was that when we went through the house,

we saw a lot of stuff

that normally would get taken in a burglary

that wasn't taken.

We saw laptops, we saw cell phones,

we saw electronic devices, televisions.

So, right from the get-go,

there was a lot of suspicion

about how this had actually occurred.

- We both felt like somebody was staging...

The murder scene to look like it was a burglary

to throw us off the trail.

It was my opinion that

kathy blair was targeted for the murder.

- crime scene investigators work late into the night,

looking for any piece of evidence

that could point them towards the killer.

- In this case, there was very little

to tell us who the murderer was.

We didn't find any dna.

We didn't find any unidentified fingerprints.

And nothing that we could just compare to a person

and say, "this person did it."

one thing we did find was...

Shoe impressions.

The person who left these shoe prints

had stepped in kathy blair's blood

and then walked around the house.

- The forensic team sends the shoe prints

to the lab for analysis,

but the lack of evidence

gets the case off to a difficult start.

- This looked like it was gonna be

a tough murder to solve.

while technicians continue

to work through the crime scene,

detectives head outside to talk to the victim's son.

He said he was staying

at his mother kathy blair's home

because he was taking a break from the navy.

He was out the night before at a christmas party,

that he and some buddies had a good time.

They slept over at the party.

He came home the next day

and discovers his mom on the floor

in a pool of blood.

- detectives rush to verify the alibi,

reaching out to the friends where the son spent the night.

Clearly, in a murder case,

you're gonna start close to the victim,

and you're gonna work your way out.

But we're quickly able to eliminate the son.

- the next day, detectives track down kathy's friends,

hoping to find out more about their victim.

They learn that kathy is a strong woman

who is both admired and loved.

- Kathy blair was a california girl who moved to texas,

had a deep passion for music,

went down a path of teaching.

- she was very well-known locally

because she was a choir teacher.

she had hundreds of current and former students.

- I was kathy's student for about four years.

Kathy's personality was very...

Forceful.

She was always driven, always determined.

She always had something to do.

as a teenager, having her there as a role model

and a parental figure meant...

Just absolute worlds to me.

I have literally no idea

what my life would look like without her.

but there may be someone

who could imagine life without kathy...

Her ex-husband.

Detectives learn their relationship was bitter.

and since their divorce four years ago,

it had only gotten worse.

- Everybody was telling us that...

Their divorce was contentious and that...

Where kathy was living was meant to be

a place that her ex-husband would never find.

kathy had asked her landlord and her friends

not to let her ex-husband know where her new house was.

So we definitely had to talk to him

and find out whether or not he was involved in this

or not.

- there was a neighbor outside early in the morning

on the night that kathy blair is killed.

- I saw the headlights coming from a car behind me.

and I was like...

"what kind of car was that?"

- 53-year-old choir teacher kathy blair

has been murdered in her bed.

Homicide detectives in austin, texas,

have zeroed in on her ex-husband

as a person of interest.

- the relationship between kathy blair and her ex-husband

had ended acrimoniously.

She had made a point

of making sure he didn't know where she lived.

So we go out to visit kathy's ex-husband.

- Kathy's ex lives outside the austin city limits.

we knocked on the door,

and I said, "I'm detective scanlon.

"I'm with the austin police department.

I'm here to tell you that kathy's dead."

his first words to me were...

"was she shot?"

it really threw me back because...

I would think most people would ask, "what happened?"

but, I mean, he, like, jumped straight

to a method of homicide.

I asked him,

"do you know anybody that would want to harm kathy?"

his answers are, "no."

and I asked him, "what about yourself?"

he answered me definitively, no, he was not involved.

his alibi was that he was camping at an rv park.

- Police ask if they can look inside the house.

To their surprise, their suspect easily agrees.

- Kathy blair's ex-husband seemed, to me,

overly cooperative.

A lot of times, I think that that's somebody

who's trying to cover up.

I searched through his house

for anything that looked like it might be

related to the crime,

and I didn't-- I didn't find anything.

Did I eliminate him on the spot right there?

No.

the day after the murder,

detectives meet with the medical examiner,

hoping his report can give them a lead.

the report can't pinpoint the time of death

but confirms that kathy was killed overnight.

- At some point, we don't know exactly what time in the night,

she was murdered in her bed.

- It was really kind of striking.

Most burglaries happen during the day when nobody's at home.

- and the cause of death was sharp force injuries.

there were, what we would refer to as,