Forensic Investigative Genetic Genealogy (FIGG) has transformed how law enforcement solves cold cases and identifies unknown individuals. This innovative method relies on DNA to uncover family connections and build genealogical trees.
But the success of FIGG hinges on using the right type of DNA testing. While traditional Short Tandem Repeat (STR) profiles have been the cornerstone of forensic investigations for years, Single Nucleotide Polymorphism (SNP) profiles are the powerhouse behind FIGG.
Here’s a closer look at why SNP profiles are required for FIGG. To learn more about FIGG, check out this recent webinar.
STR Profiles: The Workhorse of Traditional Forensics
STR testing analyzes short, repeating sequences in DNA. These patterns, unique to each individual, make STRs ideal for direct comparisons. For example:
- CODIS Database Searches: Matching DNA from a crime scene to a known individual or to other crime scene samples in the FBI’s database.
- Direct Comparisons: Verifying whether a suspect’s DNA matches evidence from a crime scene.
However, STR profiles are limited in scope. With only about 20 markers analyzed, they’re excellent for direct matches but not detailed enough for identifying distant relatives or constructing family trees—critical components of FIGG.
SNP Profiles: The Engine Behind FIGG
SNP testing focuses on tiny variations at individual points in the DNA sequence. These variations, called single nucleotide polymorphisms, provide a detailed genetic roadmap. Unlike STRs, SNP profiles examine hundreds of thousands or even millions of data points.
Why SNPs Are Required for FIGG:
- Tracing Family Relationships: SNP profiles can identify relatives as distant as third or fourth cousins, allowing investigators to build family trees.
- Comprehensive Genetic Detail: The vast number of data points gives a clearer picture of someone’s ancestry and connections.
- Integration with Genealogical Tools: Platforms like GEDmatch PRO™ are built around SNP data, enabling seamless matching and analysis.
For example, GEDmatch PRO™—a genealogical database designed specifically for law enforcement—uses SNP profiles to compare DNA evidence against a database of consenting participants, helping investigators connect genetic dots that STRs can’t reach. Learn more about GEDmatch PRO in this blog post.
STR vs. SNP: A Real-World Example
During the webinar, we explored how SNP profiles solved a decades-old cold case. Investigators used SNP testing to identify distant relatives of a person whose DNA was found at the crime scene. They built a family tree using genealogical tools like GEDmatch PRO™, eventually pinpointing the suspect.
If investigators had relied solely on STR testing, the case would likely have remained unsolved. STRs are great for direct matches and were used to confirm the DNA match in this case, but they lack the depth to reveal extended family connections or ancestry.
Why STR Profiles Still Matter
While SNPs are the cornerstone of FIGG, STR profiles still play an important role in forensic investigations. For instance, STRs can:
- Quickly confirm if a DNA sample has probative value.
- Provide leads through CODIS when a direct match is available.
Think of STRs as a precise snapshot of one person, while SNPs are a panoramic view of their entire family history. Together, these tools offer a comprehensive approach to solving cases.
Bridging Science and Investigation
FIGG is about more than just technology—it’s about using the right tools to uncover answers. For law enforcement, understanding the strengths of SNP testing opens doors to solving cases once thought impossible.
By leveraging SNP profiles and tools like GEDmatch PRO™, agencies can tap into a powerful new way of connecting the dots. Whether it’s identifying a long-lost victim or solving a cold case, FIGG has proven time and again that the right approach makes all the difference.
For more insights on FIGG and how DNA technology is advancing investigations, visit Bode Technology’s blog.