Historically, the fields of genomics
Discover the fascinating field of Forensic Science, the application of scientific principles to legal matters. This post delves into its many disciplines, from DNA analysis to crime scene investigation, its importance in the justice system, Read Full Definition have traveled along separate paths. Genomics focused on sequencing vast amounts of the human genome, while forensics relied on typing a small, preselected panel of Short Tandem Repeats (STRs). While STR profiling is highly effective for direct identification, its utility is limited when no direct match exists in a database like CODIS. A crucial comment published in Genome Biology argues that this era is over: the integration of Massively Parallel Sequencing (MPS) and Forensic Genetic Genealogy (FGG) using Single Nucleotide PolymorphismsA single nucleotide polymorphism, or SNP (pronounced "snip"), is a variation at a single position in a DNA sequence among individuals. Read Full Definition (SNPs) is not just an advancement—it is a force multiplier that will fundamentally reshape criminal justice.
SNPs vs. STRs: The Force Multiplier Effect
The foundational difference between the old and new approach lies in the amount of data
Information in analog or digital form that can be transmitted or processed. Read Full Definition analyzed. STRs provide a highly unique, but limited, genetic fingerprint. Dense SNP testing provides a vastly richer dataset of hundreds of thousands of genetic markers, fundamentally expanding forensic capabilities:
- Stability and Degradation: SNPs are more stable and can be detected in smaller DNA
DNA, or Deoxyribonucleic Acid, is the genetic material found in cells, composed of a double helix structure. It serves as the genetic blueprint for all living organisms. Read Full Definition fragments than STRs. This makes them particularly useful for analyzing degraded forensic samples that would otherwise yield incomplete or unusable STR data. - Investigative Leads: Unlike STR profiles, which primarily offer identity information, SNP data enables biogeographical ancestry inference and forensic DNA phenotyping (predicting physical traits like eye color or face shape). This provides additional context about an unknown individual, which helps focus investigative efforts.
Forensic Genetic Genealogy: Beyond the Database
Forensic Genetic Genealogy (FGG) is the primary catalyst
A catalyst is a substance that increases the speed of a chemical reaction without being consumed in the process. In forensics, it's the principle behind tests like the luminol reaction, where iron in blood catalyzes Read Full Definition for the adoption of MPS in forensics. FGG leverages the dense data from SNP testing to solve cases that STR typing was never designed to handle.
Inferring Kinship and Ancestry
Because FGG uses a very large number of SNPs, kinship associations can be inferred well beyond the first-degree relationships (parent-child or sibling) to which STRs are typically limited. This allows investigators to establish familial connections across multiple generations through pedigree development and the location of most likely common ancestors. This is essential for the countless cases where the perpetrator or unknown victim is not in a database like CODIS.
Leveraging Ancient DNA Techniques
Working with compromised evidenceEvidence is any form of proof, such as objects, materials, or scientific findings, presented to establish or disprove a fact in a legal proceeding. It is used to reconstruct events and link or exclude individuals Read Full Definition is a major issue in forensic science. The success of FGG is directly linked to the application of sophisticated extraction and analysis techniques developed in ancient DNA (aDNA) research. Methods designed to recover and analyze fragmented DNA that is thousands of years old are now being directly applied to compromised forensic samples, drastically increasing the chances of recovering a usable genetic profile.
Expert Commentary: The Moral and Economic Imperative
The paper argues that the transition to genomic methods is no longer a question of if, but when, driven by both moral responsibility and economic necessity.
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Cost-Effectiveness vs. Cost-Per-Sample
While Whole Genome Sequencing (WGS) may be more expensive than STR profiling on a simple per-sample reagent basis, the paper argues this comparison is misleading. The true measure is cost-effectiveness. The ability of FGG and SNP testing to solve decades-old cold cases and identify serial perpetrators early in their offending history provides immense long-term savings—tangible and intangible—that are estimated to be in the billions of dollars.
The Path to Full Automation
The paper highlights that genomic sequencing is highly amenable to automation and scaled analysis, which offers significant advantages over manual, capillary electrophoresis-based STR analysis. This ability to automate downstream SNP marker analysis will drive a move toward greater objectivity and throughput, creating auditable outputs and reducing reliance on subjective expert interpretation.
My Perspective: Embracing the Future of DNA Analysis
As a Senior DNA analystA designated person who examines and analyzes seized drugs or related materials, or directs such examinations to be done; independently has access to unsealed evidence in order to remove samples from the evidentiary material for Read Full Definition experienced in STR DNA analysis, I recognize the limitations of our current core methodology for the most challenging cases. STRs are fast and reliable for direct matches, but they are insufficient for the hundreds of thousands of unsolved cases left behind. This paper correctly identifies that our field must embrace genomics not only because the technology allows it, but because victims and their families deserve answers. FGG and SNP testing provide a genomic solution to the limits of STR typing. The path forward requires commitment and investment, but the reward—that no case is left unresolved—is immeasurable.
Conclusion
The integration of genomics into forensic science via Dense SNP testing and Forensic Genetic Genealogy represents a fundamental and necessary shift for the criminal justice system. By leveraging techniques pioneered in aDNA research, forensic labs can overcome the inherent limitations of STR profiling, analyze highly degraded forensic samples, and generate crucial investigative leads through kinship, ancestry, and phenotyping analysis. This transition provides a powerful tool to address the vast number of unsolved violent crimes and unidentified human remains, ensuring justice is delivered at a scale previously unimaginable.
Original Research Paper:
Budowle, B., Mittelman, K. & Mittelman, D. (2025). Genomics will forever reshape forensic science and criminal justice. Genome Biology, 26, 296. https://doi.org/10.1186/s13059-025-03798-x
Term Definitions
- Ancient DNA (aDNA): DNA recovered from historical, archaeological, or fossil remains. Techniques developed for aDNA are now used to analyze fragmented forensic samples.
- Biogeographical Ancestry Inference: The process of estimating an individual’s genetic origins or population affinity using SNP data.
- CODIS (Combined DNA Index System): The national database of STR profiles in the United States.
- Forensic DNA Phenotyping: The process of predicting an individual’s externally visible physical traits (e.g., eye color, hair color) from their DNA.
- Forensic Genetic Genealogy (FGG): A subdiscipline that uses dense SNP data, combined with genealogical databases, to identify unknown individuals through kinship inference.
- Genomics: The large-scale study of the complete genetic material (genome) of an organism.
- Massively Parallel Sequencing (MPS): Also known as Next-Generation Sequencing (NGS); a high-throughput technology that sequences millions of DNA fragments simultaneously.
- Single Nucleotide Polymorphism (SNP): A variation at a single position in a DNA sequence. Dense SNP testing is the core of FGG.
- Short Tandem RepeatA short tandem repeat is a microsatellite with repeat units that are 2 to 7 base pairs in length, with the number of repeats varying among individuals, making STRs effective for human identification purposes Read Full Definition (STR) Profiling: The traditional method for DNA profiling
- Whole Genome Sequencing (WGS): A process that determines the complete DNA sequence of an organism’s genome.
