- I've always wanted to take one of these at home DNA tests
'cause I wanna learn more about my family's background
and they're super cheap so I figured why not?
- And I have no interest in these tests.
I think it's really creepy
for some company to have my private DNA.
Either way at home tests like 23 and Me
or Ancestry DNA have exploded in popularity.
By one estimate, around 26 million people
have taken one of these tests.
- So maybe I should be worried about my privacy because
my DNA is getting uploaded to some database somewhere.
- But here's the scary thing, even if I refuse
to ever take one of these tests,
my DNA could be at risk, too.
The reason why starts with a serial killer.
Our colleague Rachel explained it to us.
- So the Golden State Killer
is also known as the East Area Rapist
and in the 1970s and 80s he raped
and murdered people across California.
- He was wearing some type of a mask or hood.
- [Rachel] And for decades, investigators
just had no idea who he was.
- Their was some DNA left at crime scenes,
but even after decades investigators
couldn't find a suspect so they had
nothing to compare the DNA to.
But all that changed in 2018.
- So the big break through came
when investigators uploaded genetic profile
from the crime scene DNA to this
big, huge genealogical database.
They didn't find an exact match,
but they did find matches to relatives.
- [William] Investigators used a method
called a long-range familial search
to find similarities between the crime scene DNA
and a few of that person's third cousins.
From there they could narrow their search way down
and look for a suspect within a specific
family tree and they found one.
- The answer was and always was going to be in the DNA.
- [William] Investigators solved the case
because of the big DNA database they used
which didn't belong to law enforcement.
It's freely available and they data inside it
came from services like 23 and Me.
An at home DNA test like 23 and Me
generally works by looking at spots in your genome
called Single Nucleotide Polymorphisms or SNPs.
Each one is a specific location
where there are known variations from person to person.
Companies make their guesses about your ancestry
by analyzing thousands or even millions of SNPs.
Populations in Europe, say, are more likely
to have one set of variations,
whereas Asian populations might have a different set.
For an end user like Danush this is the product being sold,
a map of his ancestral stomping grounds.
- I got 86.7% Western Asian which on the map
is highlighting Turkey, Iran, Iraq, that part of the world.
- But underneath the UI is the raw data.
The log of all those SNPs.
That data ends up in a private data base
owned by whoever sold you the test kit.
Now here's where it gets interesting.
Investigators working a case
have a few options for doing a genetic search.
First they could search through a testing company's
private database if they can gain access.
Family Tree DNA was in the news recently
for actively working with law enforcement.
23 and Me says that it won't do that,
but there's always the threat of a court order.
So that route is tricky.
Second, the FBI does operate a national DNA index
with around 17 million identified people in it.
And some states allow the index
to be used for familial searches.
But those 17 million people are all arrestees and offenders.
So unless the suspect had relatives
in the criminal system it's not much help.
But investigators in the Golden State
Killer case found a third option.
More and more, customers of DNA services
are voluntarily posting their genetic profiles
on free to search websites like GEDmatch,
DNA Land, or Family Tree DNA.
This is great for anyone doing
genealogy or looking for long lost relatives.
With a few clicks on GED Match,
you can create an account, upload your DNA profile,
and maybe find a bunch of third
cousins you never knew about.
But it was also great for investigators
tracking the Golden State Killer.
- So law enforcement used it in a similar way.
They took the crime scene DNA,
created a fake profile and uploaded it,
and then looked for relatives.
- That was the break through.
They used DNA info that was freely available.
No need for subpoenas or criminal databases,
it's just sitting there, but this is
where my privacy is at stake.
Let's go back to that big web of third cousins.
It was used to catch a serial killer, that's great.
But instead of crime scene DNA, swap in my DNA.
I leave my DNA all over the place.
I shed hair, skin cells, saliva,
but I've never gotten my DNA sequenced.
So I shouldn't have anything to worry about.
But through familial testing, if enough of my relatives
took tests I could be identified from a DNA sample
just like the Golden State Killer was.
Now I'm not planning on committing any crimes,
but there are still privacy concerns for me.
First, false positives exist in DNA tests.
So I could end up the subject
of an investigation by mistake.
Or a sketchy insurance company could find a way
to correlate some of my genetic data
with other medical information and discriminate against me.
We asked a genetic privacy expert
Natalie Ram about these concerns,
and she said that the unifying problem is control.
- [Natalie] Your genetic data is a link
that you share with family members involuntarily.
It's not something I've chosen,
and it's something I cannot change.
- And to up the anty, as databases grow,
more and more people will be findable
by their hundreds and hundreds of distant relatives.
- [Natalie] And then you've gotta ask, gosh,
how many third cousins do I have?
Do I even know who all those people are?
- A recent study assigned some pretty
surprising hard numbers to this.
It predicts that for any population
that shares some common ancestry,
having DNA from just 2% of the people
could make anyone findable via a third cousin or closer.
For example, all Americans with some European ancestry
could be matched from just a 2% pool.
So if free databases get diverse enough,
everyone in America could be findable via their genes.
Which means DNA just won't be anonymous anymore.
- [Natalie] The bottom line here
is that we are rapidly approaching a place
where we have a defacto national DNA database.
- For now lots of people are debating policies
that would regulate familial search.
One law proposed in Maryland would completely
ban familial DNA searches of consumer databases.
A more extreme policy could create
an official nationwide DNA database.
That sounds creepy, but it might be easier
to regulate than the defacto system we're headed for.
In the meantime, while we debate all these questions,
piles and piles of at home DNA test kits are sold.
The database continues to grow,
and the genetic drag net grows too.
Hey so we made this video in collaboration with vox.com,
and Danush has made a companion
video that you should check out.
- Yeah so our video looks into how these DNA tests
actually work and what they can and can't tell you.
So make sure to go check that one out.
- Yep watch it now, it'll be right over there, I think.
- Smash that like button. - Gross.