Unlocking Justice: AI’s Role in Cold Case Investigations

Solving Cold Cases with AI and Genetic Genealogy

For decades, cold cases have haunted investigators, victims’ families, and communities. These are the unsolved murders, assaults, and disappearances that grow colder with each passing year as evidence degrades, witnesses fade, and suspects vanish into obscurity. Each box of files sitting in a police evidence room represents unanswered questions—and families waiting for closure that may never come.

Now, a breakthrough is changing that narrative. The combination of artificial intelligence (AI) and genetic genealogy is breathing new life into these forgotten investigations. With the ability to scan millions of DNA records in hours, reconstruct family trees in weeks instead of years, and uncover hidden patterns in old evidence, AI is giving investigators tools that once seemed like science fiction.

This isn’t just an upgrade in forensic technology—it’s a revolution. The same advances that power modern medicine, search engines, and machine learning are now helping law enforcement bring justice to crimes long thought unsolvable. The question is no longer if cold cases can be solved, but how quickly and affordably AI can help close them.

The Role of DNA in Cold Cases

DNA evidence revolutionized forensic science. Since the 1980s, even the smallest biological sample—blood, saliva, hair—could identify or exclude a suspect with extraordinary precision. For many years, this represented the gold standard in criminal investigation.

But in cold cases, DNA alone is often not enough. Traditional forensic methods rely on direct matches: the crime scene DNA must match someone already in a law enforcement database (such as CODIS in the U.S.). If the suspect was never arrested, convicted, or had their DNA collected, investigators hit a dead end. For decades, thousands of cases languished simply because the right profile wasn’t in the system.

This is where genetic genealogy changes the equation. Instead of looking for a direct match, investigators can compare DNA samples from a crime scene with profiles voluntarily submitted to public genealogy databases. Even if the suspect isn’t in the database, their relatives might be.

By finding distant relatives—second, third, or even fourth cousins—investigators can build family trees that stretch back generations. Through process of elimination and genealogical research, these trees can be narrowed down until only a handful of individuals fit the right location, age, and timeline. Suddenly, cases that were dormant for 30 or 40 years can be revived with new, highly targeted leads.

This approach has already led to hundreds of solved cases, including the Golden State Killer, Jay Cook and Tanya Van Cuylenborg murders, and the identification of the Buckskin Girl. But genealogy is only one piece of the puzzle. Other cold case evidence—fingerprints, ballistics, photographs, videos—can also hold answers if examined with fresh eyes.

How AI Transforms the Process

While genetic genealogy has already solved high-profile cases, AI amplifies its effectiveness in four major ways:

1. DNA Analysis Acceleration
   • AI rapidly scans millions of DNA profiles, identifying partial or familial matches.
   • It can predict likely family relationships (e.g., “3rd cousin once removed”) with high accuracy.
2. Automated Family Tree Construction
   • AI builds large family trees by linking genetic matches with public records (census data, obituaries, marriage certificates, property records, even social media).
   • This reduces months of genealogist work to weeks or even days.
3. Pattern Recognition in Evidence
   • AI re-examines old forensic material such as fingerprints, handwriting, and ballistics.
   • Modern recognition algorithms succeed where older tools failed, uncovering missed connections.
4. Case Prioritization
   • AI clusters unsolved cases that share genetic or geographic patterns.
   • This helps agencies focus limited resources on the cases most likely to be solved.

Workflow: From DNA to Arrest

The process typically follows these steps:

1. Cold Case DNA Evidence – Crime scene samples are secured and digitized.
2. DNA Sequencing & Profile Creation – Profiles are generated for compatibility with genealogy databases.
3. AI DNA Matching – AI finds distant relatives, often 2nd–4th cousins.
4. Genetic Genealogy Research – Family trees are built using AI and genealogists.
5. Suspect Narrowing – Filters such as location, age, and timelines reduce the candidate pool.
6. Cross-Checking with Other Evidence – Fingerprints, ballistics, and witness reports confirm alignment.
7. Law Enforcement Review & Arrest – Confirmatory DNA is collected, and arrests are made.

Real-World Example: The Golden State Killer

Few cases demonstrate the power of genetic genealogy more dramatically than the hunt for the Golden State Killer. Between 1974 and 1986, a single offender terrorized California with a string of over 50 rapes and 13 murders. He stalked neighborhoods, broke into homes, and left behind a legacy of fear that lingered for decades. Despite extensive investigation, the case went cold. DNA evidence existed—but the man behind it was not in any criminal database.

For more than 40 years, the Golden State Killer was a ghost.

Then, in 2018, investigators tried something bold: they uploaded DNA from old crime scenes into a public genealogy database. Instead of searching for a direct match, they searched for distant relatives—cousins, second cousins, and beyond. With painstaking genealogical research, they built sprawling family trees going back generations. Slowly, they whittled down thousands of potential names to just a few men who fit the right time, place, and profile.

One of those men was Joseph James DeAngelo—a former police officer living quietly in a Sacramento suburb. Investigators collected a discarded tissue from his trash and tested it. The DNA matched. After four decades of mystery, the Golden State Killer had a name, a face, and a pair of handcuffs around his wrists.

Why This Case Matters

• It was the first high-profile proof that genealogy could solve crimes long thought unsolvable.
• It showed that justice delayed does not have to mean justice denied.
• It sparked a wave of similar investigations, leading to hundreds of other cold case breakthroughs across the U.S.

But it also exposed the limitations of manual work. Genealogists spent months building out family trees by hand, poring over census data, obituaries, and marriage records. The process was slow, labor-intensive, and expensive.

What AI Could Change with today’s AI tools

• The DNA search could be completed in hours, not weeks.
• Family tree construction—once requiring genealogists to manually connect hundreds of dots—could be automated in days.
• Cross-referencing age, geography, and public records could instantly narrow the field to the most likely suspects.

Lisa’s Story (aka “Dawn Identity”) (New Hampshire, 1981–2000s)

What once took decades of waiting and months of manual analysis could now be reduced to a matter of weeks at a fraction of the cost.

A woman living under false identities across the U.S. was revealed through genetic genealogy to be “Lisa,” a kidnapped child, and connected to the “Bear Brook murders.” The suspect, Terry Rasmussen, was posthumously identified as responsible.

AI impact: AI cross-matching genealogy with missing children’s records could make such identity untangling faster and more routine.

The Buckskin Girl (Ohio, 1981)

An unidentified young woman found wearing a distinctive buckskin poncho became known as “Buckskin Girl.” She remained nameless for decades until 2018, when genealogy identified her as Marcia King from Arkansas.

AI impact: With computer vision and AI record linkage, such victim identifications could scale—connecting old photos, clothing brands, and missing persons reports in hours.

The Cost Barrier and How AI Democratizes Cold Case Analysis

Cold case investigations have traditionally been prohibitively expensive, often costing $50,000 to $150,000 or more per case. These costs come from:

• Hiring specialized forensic genealogists for hundreds of hours of labor.
• Paying for repeated lab tests, fingerprint or ballistics analysis, and expert consultations.
• Traveling to collect records, conduct interviews, and follow leads that may end in dead ends.

For large metropolitan departments, these costs are sometimes manageable, especially for high-profile cases. But for smaller police departments—which make up the majority of U.S. law enforcement—budgets are far more constrained. Many agencies struggle to keep up with day-to-day caseloads, let alone allocate six figures to a decades-old investigation.

As a result, thousands of cold cases remain untouched, not because they are unsolvable, but because the resources required are out of reach. Justice, in these cases, becomes a privilege of funding.

AI as a Force for Democratization

Instead of teams of investigators spending months buried in paperwork and endless database queries, AI takes on the heavy lifting—scanning millions of DNA profiles in hours, assembling sprawling family trees in days, and cross-checking evidence across forensic databases at a scale no human team could match. The result? Cold case investigations that once drained budgets and manpower can now be done faster, smarter, and at a fraction of the cost.

• Automated DNA matching: Cuts weeks of manual genealogist work down to hours of compute time.
• AI-driven family trees: Replaces hundreds of hours of genealogical record digging.
• Computer vision re-analysis: Allows old evidence to be re-examined digitally, instead of requiring costly lab rework.

Instead of $100,000+ per case, AI-assisted workflows can bring costs down to $10,000–$25,000—a level where even small-town police departments can consider reopening long-dormant cases.

Why This Matters

AI doesn’t just make cold case investigation faster and cheaper—it makes it accessible. This democratization means:

• Victims in smaller communities are no longer left behind.
• Families who have waited decades in silence may finally get answers.
• Justice is no longer dictated by a department’s budget size, but by its willingness to adopt new tools.

AI vs. Human Timelines

Task	Human-Led Approach	AI-Assisted Approach	Speed Advantage
DNA Database Scan (millions of profiles)	Weeks–Months	Hours–Days	10×–50× faster
Family Tree Construction (200–1,000 relatives)	3–6 months	1–2 weeks	~10× faster
Case Prioritization Across Cold Cases	Rarely feasible	Minutes	~100× faster
Evidence Re-analysis (fingerprints, ballistics, etc.)	Weeks per dataset	Hours	10×–20× faster

Bottom Line: A cold case investigation that might drag on for 6–12 months manually can often be reduced to just 2–6 weeks with AI support.

AI vs. Human Cost Comparison

Task	Human-Led Cost	AI-Assisted Cost	Cost Advantage
Genealogist Labor (100–500 hours)	$25,000–$100,000+	$2,000–$10,000	5×–10× cheaper
Record Retrieval (manual lookups, travel)	$5,000–$20,000	Mostly automated	3×–5× cheaper
Multi-Case Prioritization	Millions in staffing	$20k–$50k annually	20× cheaper
Total Investigation Cost (per case)	$50,000–$150,000+	$10,000–$25,000	4×–6× cheaper

Ethical and Privacy Considerations

The rise of AI and genetic genealogy brings unprecedented opportunities—but also profound responsibilities. As with any powerful tool, misuse can erode public trust and cause unintended harm. To ensure these technologies serve justice without overstepping boundaries, several principles must guide their use:

Respect for Consent and Database Policies

Not all genealogy databases permit law enforcement use. Agencies must respect the terms of service and only access those where users have explicitly opted in. Violating this principle risks public backlash and could undermine the willingness of individuals to share DNA data at all.

Protection of Innocent Relatives

Genetic genealogy often identifies relatives, not suspects. These individuals are overwhelmingly innocent and should not be treated as targets. Investigators must handle their data with care, protect their privacy, and avoid public exposure unless absolutely necessary.

AI as a Partner, Not a Judge

AI should function as a decision-support system, not as the final arbiter of guilt or innocence. Algorithms can flag leads, prioritize cases, and uncover hidden links—but only trained investigators can interpret that information in the full context of human behavior, law, and ethics.

Avoiding Bias and Over-Reliance

AI systems are only as good as the data they’re trained on. If databases are incomplete, skewed, or biased, results may disproportionately impact certain populations. Constant auditing, transparency, and human review are critical to prevent misuse or misinterpretation.

Safeguarding Data Security

Genetic data is among the most sensitive information a person can share. Strict security protocols, encryption, and controlled access are essential to prevent breaches or unauthorized use. Trust is the foundation of public cooperation in solving cold cases.

Why Ethics Matter

The promise of AI and genetic genealogy is extraordinary: solving cases once thought unsolvable. But public trust is fragile. A single misstep, such as using data without consent or targeting innocent relatives—can spark outrage and jeopardize the future of these tools.

Handled responsibly, however, these technologies offer a rare chance to expand justice while respecting rights. The goal must always be twofold: deliver answers to families while protecting the dignity and privacy of everyone involved.

Conclusion

The fusion of AI and genetic genealogy isn’t just a new tool in the forensic toolbox, it’s a paradigm shift in justice itself. What once demanded years of painstaking labor, six-figure budgets, and entire teams of specialists can now be achieved in weeks, at a fraction of the cost. And the impact isn’t measured in efficiency alone—it’s measured in lives. Every case solved means a victim remembered, a family finally answered, and a community reminded that justice never truly expires. For law enforcement, the debate is over. The only question left is how fast these tools can be deployed. For families who have waited decades, every day saved is priceless. And for suspects who thought the passage of time would shield them, AI is delivering a sobering message: the past is no longer safe harbor.

Final Thought: Cold cases aren’t cold anymore. With AI and genetic genealogy, justice delayed no longer means justice denied.