Cold Case DNA & Investigative Genetic Genealogy: How Modern Forensics Solves Old Cases

Investigative genetic genealogy identified the Golden State Killer in 2018 after more than four decades. The technique has changed what is possible in cold case investigation. Cases once considered permanently unsolvable are now being closed. This article explains how the technology works, which cases are candidates, and what it takes to use it.

The Baseline: Traditional Cold Case DNA Analysis

Before the genetic genealogy revolution, cold case DNA work was already powerful. It remains the first step. Preserved biological evidence such as blood, semen, skin cells, or hair with roots can be tested using modern STR analysis. The results are then compared against CODIS, the FBI's national DNA database. Hits on CODIS identify suspects already in the system, usually because of a prior conviction or arrest.

This technique solves most cold case DNA matches. It requires that the suspect's profile is already in a criminal database. When the suspect has never been in the system, CODIS cannot help.

What Investigative Genetic Genealogy Adds

Investigative genetic genealogy (IGG) uses consumer DNA databases instead of criminal databases. The main sources are GEDmatch and FamilyTreeDNA's opt-in investigative pools. Instead of matching a suspect directly, IGG matches the suspect's DNA against relatives who have voluntarily uploaded their genetic profiles.

Once a relative match is found, even a third or fourth cousin, a genealogist builds a family tree outward from that match. The work draws on marriage and birth records, obituaries, public records, and traditional genealogical research until a set of candidates emerges. Traditional investigation then narrows that set to a single person, usually through elimination and confirmatory DNA testing.

This is how cases with no suspect in any criminal database can now be solved. The suspect does not need to be in the system. One of their cousins does.

Which Cases Are Candidates for IGG

Not every cold case can use investigative genetic genealogy. The prerequisites:

• Preserved biological evidence in workable condition. Blood, semen, saliva, tissue, or hair with roots. The evidence needs to be sufficient quantity and quality to extract a full DNA profile for SNP microarray testing, which IGG requires rather than the STR profile that CODIS uses.
• Known chain of custody for the evidence. The evidence has to be demonstrably from the crime and not contaminated.
• A case with no known suspect, or a suspect pool that CODIS has not resolved. IGG is used specifically where traditional DNA matching has not worked.
• Legal and procedural authority to pursue IGG. Policy varies by jurisdiction. Some agencies pursue IGG routinely; others require a prosecutor's approval or specific circumstances.

Cases without preserved biological evidence cannot use IGG. Unfortunately, this describes most old cold cases. That is why IGG, for all its power, has not made cold case investigation obsolete.

The Cost and Timeline

IGG analysis is expensive. A full investigative genetic genealogy workup typically costs $5,000 to $25,000 per case. That total covers SNP microarray testing, genealogist work, and confirmatory testing. Specialty forensic labs like Othram handle a large share of the work and charge accordingly.

Timelines range from a few months to a year. The variability depends almost entirely on how close the match is. A first cousin match can resolve in days. A fifth cousin match may take months of tree-building before a candidate emerges.

Working IGG Into a Cold Case Investigation

For families pursuing a cold case through private investigation, IGG is sometimes recommended and sometimes not. A qualified cold case investigator will:

• Confirm that preserved biological evidence exists and can be located
• Determine whether law enforcement has already attempted traditional DNA matching and IGG
• Advise on the cost-benefit of pursuing IGG when the agency has not
• Coordinate with a specialty lab and genealogist if IGG is appropriate

For cases where IGG is the right tool, the combination of a motivated family, a qualified private investigator, and a specialty forensic lab has produced some of the most dramatic cold case resolutions of the past decade. It is not a universal solution. For the cases it fits, nothing else comes close.

The Ethical Frame

Investigative genetic genealogy is powerful because it uses DNA that people voluntarily uploaded for their own purposes. The consent model, law enforcement access policies, and constitutional questions around IGG are still evolving. Reasonable people disagree about where the limits should be. A qualified investigator stays inside current legal and ethical practice. That means working only with databases that explicitly permit law enforcement use, and working through a specialty lab rather than running the analysis informally.

Encyphir's cold case investigators coordinate IGG workups with specialty forensic labs. We work alongside our digital forensics team and litigation support attorneys when a match develops into a case that prosecutors can move on.

Locating and Re-Examining the Evidence

Before any DNA analysis can happen, the physical evidence must be found. This is where many private cold case inquiries stall. Evidence from a case that went cold in the 1970s, 1980s, or 1990s may be sitting in any number of places:

• A police property room
• A medical examiner's long-term storage facility
• A hospital pathology archive
• A retired detective's case file box

Over the decades, agency mergers, building moves, retention purges, and simple human error have lost more evidence than most families realize.

A qualified cold case investigator begins with a systematic evidence inventory. That means requesting the original case file under state open records statutes or through family liaison channels. The investigator then identifies every item of potential biological significance collected at the scene or during autopsy, and traces each item to its current storage location. Rape kits, slides from sexual assault examinations, autopsy tissue blocks, clothing cuttings, and swabs from under fingernails are all candidates. Evidence that was never tested for DNA at the time, because the case predates DNA technology or because prosecutors declined to pursue testing, is often the most productive to revisit.

Preservation condition matters as much as existence. Evidence stored at room temperature in a humid basement for forty years is not the same as evidence held in climate-controlled storage. A good lab will assess viability before charging for a full workup. An experienced investigator will prepare the family for the realistic possibility that the evidence exists but is too degraded to produce a usable profile.

Coordinating With Law Enforcement and Prosecutors

IGG almost never operates outside a law enforcement framework. The analysis may be conducted at a private lab and funded by a family. But the resulting lead has to be handed to investigators with arrest authority, and eventually to a prosecutor willing to file charges. A private investigator who understands this builds the working relationship early rather than presenting a finished package to a skeptical agency.

In practice, this means several things:

• Briefing the original investigating agency on the intent to pursue IGG
• Getting formal evidence release or sampling authority
• Agreeing in advance on how confirmatory testing will be conducted once a candidate emerges

Some agencies are enthusiastic partners. Others are institutionally cautious and will require persistent, respectful engagement. Law firm clients retaining Encyphir for post-conviction work, wrongful death litigation, or civil claims related to unsolved homicides can benefit from the same coordination framework. Our law firm engagement team structures these investigations to produce evidence that is admissible and court-ready.

Prosecutors want to know that the IGG lead was developed through databases that authorize law enforcement use. They also want documented genealogy work, and a confirmatory DNA match obtained lawfully. That match usually comes through a discarded DNA sample collected under established surveillance practice, or through consent.

Forensic Genealogy Beyond Cold Homicides

The public associates IGG almost exclusively with solving decades-old murders. The same technology has important applications in other investigative contexts. Unidentified human remains cases, which the National Missing and Unidentified Persons System tracks by the tens of thousands, are a significant and growing use of IGG. A set of remains recovered in 1985 with no dental match and no fingerprints on file can now be identified through the same SNP and genealogy workflow. That returns answers to families who have waited a generation.

Adoption reunification, identification of unknown biological parents, and paternity questions involving deceased putative fathers are civil-side applications. These do not involve law enforcement at all. They follow similar forensic principles but operate under different consent and privacy rules. They frequently intersect with our background investigations practice when, for example, an estate matter turns on confirming or excluding a claimed biological relationship.

Human trafficking investigations have also begun to incorporate genetic genealogy. This applies when victims cannot provide, or cannot recall, their own biographical history. In those cases, IGG becomes a tool for restoring identity rather than assigning criminal responsibility.

Managing Family Expectations Through a Long Process

Cold case work is emotionally demanding for the families who drive it. Many have waited years or decades for movement. The arrival of a plausible new technology can create expectations that the case will resolve quickly. A responsible investigator sets realistic benchmarks at the outset. Several outcomes are possible:

• Evidence may not be locatable
• Evidence may not be viable
• The match may be distant
• The genealogical tree may hit dead ends around non-paternity events or adoption
• Even a strong candidate may not produce a chargeable case if prosecutors decide the surviving evidence will not support proof beyond a reasonable doubt

Clear communication at each phase protects the family from both false hope and premature despair. Monthly status updates, written summaries of each milestone, and candid conversations when a path closes are standard practice. Families deciding whether to commit personal funds to an IGG workup deserve honest cost-benefit analysis, not a sales pitch.

Getting Started on a Cold Case

Families, attorneys, and advocacy groups considering an IGG-supported cold case review should begin with a structured intake. That intake captures the case history, the agency currently holding jurisdiction, the known status of evidence, and the goals of the engagement. From there, a scoped investigative plan can identify whether IGG is realistic, what preliminary steps are needed, and what budget range is appropriate. Encyphir accepts cold case matters through our standard client intake process. Inquiries about specific cases can be directed through our contact page for an initial confidential discussion.

The tools available to cold case investigators in 2025 are unrecognizable compared to what existed even a decade ago. For the right cases, with preserved evidence and a committed team, answers that seemed permanently out of reach are now within practical grasp.