Genetic genealogy isn't just for finding out why you have a distant cousin in Norway. It’s the most terrifying—and effective—tool in the modern investigator's kit. Honestly, if you grew up watching The New Detectives: Case Studies in Forensic Science, you remember the grainy footage of luminol and fingerprint dusting. It felt high-tech then. But the The New Detectives: Case Studies in Forensic Science family plots episodes were just a precursor to a world where a half-eaten slice of pizza or a discarded napkin from a relative can lead police straight to your door.
This isn't just about science. It’s about the messy, complicated reality of family trees.
When we talk about forensic science family plots, we are talking about a massive shift in how "cold" cases are heated back up. For decades, if a killer’s DNA wasn’t in CODIS (the Combined DNA Index System), the case usually just sat in a box in a basement. CODIS only looks at convicted offenders or known arrestees. It’s a closed loop. But the new detectives don't play by those old rules anymore. They use public databases like GEDmatch and FamilyTreeDNA. They look for your third cousin. Then your second cousin. Then they build the tree back down to you.
Why the Golden State Killer Changed Everything
The 2018 arrest of Joseph James DeAngelo was the "Big Bang" for this field. For forty years, the East Area Rapist/Golden State Killer was a ghost. Investigators had his DNA from multiple crime scenes, but he wasn't in any criminal database. He was a former cop. He knew how to stay off the radar.
Enter Paul Holes and Barbara Rae-Venter.
Venter isn't a badge-wearing detective in the traditional sense. She’s a genetic genealogist. By uploading the killer's DNA profile—painstakingly reconstructed—to GEDmatch, she found distant relatives. We are talking great-great-grandparents from the 1800s. From there, it was a brutal, manual slog of "reverse genealogy." You build the tree forward. You look for men of the right age, in the right place, at the right time.
It worked.
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They narrowed it down to DeAngelo. They followed him to a Hobby Lobby, waited for him to drop something, and grabbed his "abandoned" DNA. A 100% match. This case proved that The New Detectives: Case Studies in Forensic Science family plots weren't just TV drama; they were the new blueprint for justice.
The Science of Kinship and "Family Plots"
It’s kinda wild how much we share with people we’ve never met. You share about 50% of your DNA with a parent, but by the time you get to a third cousin, you're looking at maybe 0.78%. That sounds like nothing. To a forensic genealogist, it’s a gold mine.
How they actually do it
First, they take the degraded crime scene DNA. It’s often old. Maybe it’s been sitting in a freezer since 1974. They use Single Nucleotide Polymorphism (SNP) signaling. Unlike the old-school STR (Short Tandem Repeat) testing used in CODIS, SNP looks at hundreds of thousands of markers across the entire genome.
Once they have the profile, the "family plot" thickens. They look for "segments" of DNA that match other users.
- Identical by Descent (IBD): These are the chunks of DNA you share with someone because you both inherited them from a common ancestor.
- Centimorgans (cM): This is the unit of measurement for DNA sharing. The more cM you share, the closer the relation.
The investigators basically act like digital bounty hunters. They scour obituaries. They look at Facebook marriage announcements. They dig through 1940s census records. They are looking for that one branch of the family tree where a "person of interest" fits the physical description of the suspect.
The Ethical Quagmire Nobody Wants to Admit
Not everyone is happy about this. Privacy advocates are, frankly, terrified. When you upload your DNA to find out if you're 5% Irish, you are effectively "volunteering" the genetic privacy of your entire extended family. Your brother didn't consent to being part of a police lineup. Neither did your cousin.
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CeCe Moore, a lead investigator with Parabon NanoLabs and a frequent face on modern iterations of forensic shows, has been vocal about the "public good" vs. "private rights" debate. There have been instances where police tried to search private databases like AncestryDNA or 23andMe. For now, those companies generally fight back, requiring a warrant. But GEDmatch and FamilyTreeDNA have different "opt-in" settings for law enforcement.
The reality? Most people don't read the terms of service. They just want to see the map of Europe.
Case Study: The 1987 Jay Cook and Tanya Van Cuylenborg Murders
This one is heartbreaking. A young Canadian couple went missing during a trip to Seattle. Their bodies were found in separate locations. For 31 years, the case was ice cold.
The "new detectives" used the same methods as the DeAngelo case. They found a match on a public database that led to a specific family in Washington state. The suspect was William Earl Talbott II. He was a truck driver. He had no criminal record. He wasn't in CODIS.
When police arrested him, his mother was shocked. His neighbors were shocked. He was the "quiet guy." This is the recurring theme in The New Detectives: Case Studies in Forensic Science family plots. The science finds the people who were never "supposed" to be caught. It finds the people who blended back into society and lived "normal" lives for three decades while their victims' families suffered.
The Problem with "Inconclusive" Results
It’s not always a slam dunk. People think forensic science is like CSI where a light flashes and a face pops up on the screen. It isn't.
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Sometimes the DNA is too degraded. Sometimes the "family plot" is a "pedigree collapse"—that’s a fancy way of saying people in the family tree married their cousins, which makes the DNA matches look way closer than they actually are. It confuses the algorithms.
There’s also the issue of "contaminated" samples. If a technician sneezed near the sample in 1982, the SNP testing might pick that up. The new detectives have to be incredibly careful. One wrong branch on the genealogical tree can lead to an innocent person being hounded by police. It’s happened. In 2014, a filmmaker named Michael Usry was targeted for a 1996 murder because his father’s DNA (donated to a church-project database) was a close match. He was eventually cleared, but the trauma remained.
Looking Toward the Future of Forensics
We are moving into "Phenotyping." Companies like Parabon can now take DNA and predict what a suspect looks like. Eye color, hair color, skin tone, even the shape of their nose.
Imagine combining that with the family tree. You don't just have a name; you have a face. It’s a level of surveillance that George Orwell couldn't have dreamt up.
But for the families of the "Disappeared," this is a miracle. Every week, a new "John Doe" or "Jane Doe" gets their name back because of forensic genealogy. Bodies found in the woods in the 70s are finally being sent home.
Practical Steps for the Curious (or Concerned)
If you're fascinated by the intersection of family history and criminal justice, or if you're worried about your own "genetic footprint," here is how the landscape currently sits:
- Check your privacy settings: If you have used a DNA service, go into the settings. Look for "Law Enforcement Processing" or "Public Discovery." You can usually opt-out if you don't want your data used in these types of "family plot" investigations.
- Support the DNA Doe Project: This is a non-profit that uses these exact methods to identify unknown remains. They rely on volunteers and donations to give names back to the nameless.
- Understand the "Abandoned DNA" laws: In many jurisdictions, police do not need a warrant to pick up a cup you threw in a trash can in a public park. Once it leaves your hand and hits the bin, it’s legally "abandoned."
- Follow the Legislation: Watch for bills regarding the "Genetic Information Nondiscrimination Act" (GINA) and how they evolve to cover forensic uses. Laws are struggling to keep up with the speed of the lab work.
The era of the "perfect crime" is dying. It's not dying because of better fingerprints or faster police cars. It's dying because our families carry our secrets in their blood, and the new detectives finally figured out how to read the map.
To stay informed on the technical side of these developments, researching the specific "SNP" testing protocols used by the FBI's Investigative Genetic Genealogy (IGG) unit provides the most accurate look at how these cases move from the lab to the courtroom. The field is changing so fast that what was true six months ago is often outdated today. Keep an eye on the American Academy of Forensic Sciences (AAFS) updates for the latest peer-reviewed breakthroughs in kinship analysis.