Nancy Grace On Her True Crime Hit Bloodline Detectives

When did investigators start using genetic genealogy in these kind of investigations?

DNA, deoxyribonucleic acid, has been around for years and years. The gradual development, or refining, of DNA technology is ongoing even right now. I remember back in the sixth grade learning the word[s] "deoxyribonucleic acid," so it's been around for a long time.

However, I also recall the first case I prosecuted that used DNA. Prior to that, I had to prove rape, sodomy, murders, child molestations with, for instance, the same type of hair. I could find a hair on the victim's clothing and go, "Okay, the perp was a white male." That's all I could say. Then, the defendant would be a white male. That really doesn't help that much.

I could say the defendant's blood type is A+. That's about ... 30-40% of the population? Didn't help that much. It would have to be highly corroborated.

The first trial I used DNA is really a funny story. I told the scientist at the crime lab, "Bring everything," and they went, "Oh, you mean the pictures and the film?" I'm like, "Yes, everything."

They put that up in front of the jury. It was a female scientist, as I recall. She put it up, and it looked like someone had taken an old school camera and pulled the film out, and it was all these blurry dots. I went, "Okay, thank you for sharing that with the jury," and I immediately started taking it down while I was asking questions, because it looked like undeveloped reels of negatives.

However, scientists can look at all those dots and match it up to, for instance, one in 3 trillion likelihood you're not the murderer. So it's incredible.

On "Bloodline Detectives," which I'm super proud of, we are just starting Season 3. Season 1 and Season 2 [are] streaming. We get a chance to do something I don't always get to do unless I'm actually trying a case, and that is deep dive on forensic technology.

We're looking at genetic genealogy, such as in the DeAngelo case, the Golden State Killer. I love hearing about that case, and everyone focused on genetic genealogy because of Golden State Killer.

The way that works is, it's crazy. You may have to go back a hundred years. Let's pretend you're the murder victim. We find, right beside your body, a Krispy Kreme coffee cup with DNA on it. Yay! We've got a coffee cup with DNA, but it doesn't match anybody. We go through all the databases — GEDmatch, which is a public database through everybody that's ever been convicted, through all the government workers who have to give DNA or fingerprints. Nothing.

We go to genetic genealogy, and we keep going back, all the way to great, great, great grandparents. We sit down to find who with similar DNA was in the area at the time of the offense. Then, you start narrowing it down to potential defendants.

Then, you have to get their DNA somehow. I've had a case that we covered where the defendant, the suspect, went out for pizza, threw away his plate and left. The cops were waiting. They got a crusted pizza and they got DNA off of it and made the match.

That's how the Golden State Killer ended his reign of terror. DeAngelo had murdered and raped for years without getting caught. If it was not for genetic genealogy, he would never have been caught.