Latest Breakthroughs

Recent advances in forensic science are led by DNA: investigative genetic genealogy, rapid DNA, next-generation sequencing, and DNA phenotyping have all moved from research into real casework, most visibly with the 2018 identification of the Golden State Killer [1]. At the same time, two major reviews (the 2009 National Academy of Sciences report and the 2016 PCAST report) pushed the field to prove which methods actually hold up under scientific testing [9][10].

The short version: DNA techniques are getting faster, more sensitive, and able to work from tiny or degraded samples, while older pattern-matching methods are being sorted into what is validated and what is not. Below is what changed and where each development is documented.

How investigative genetic genealogy identified the Golden State Killer

Investigative genetic genealogy combines the genetic analysis of a crime scene sample with public genealogy databases where people have voluntarily uploaded their own DNA [1]. Instead of the short list of markers used in the national criminal database, it reads more than 500,000 single-nucleotide polymorphisms (SNPs) across the genome, then uses automated matching to find people who share long blocks of DNA with the unknown sample [1]. Those matches are usually distant relatives, and a genealogist builds family trees outward until the search points to a small set of candidates.

The case that made this public was the Golden State Killer. In April 2018, investigators uploaded a crime scene DNA profile to the genealogy site GEDmatch, found distant cousins, and used family trees along with details like age, location, and a physical description to narrow the field to Joseph James DeAngelo [2]. He was arrested that month, and the method has since been applied to many unsolved murders and unidentified remains [1].

Because the technique reaches into other people's genetic data, the Department of Justice issued an interim policy that took effect in November 2019. It limits genetic genealogy to unsolved violent crimes and unidentified remains of suspected homicide victims [1]. Plain definitions for terms like SNP and STR are in the forensic glossary.

Rapid DNA: a profile in under 90 minutes

Rapid DNA is a fully automated system that takes a cheek swab and returns a standard DNA profile in under 90 minutes, with no separate laboratory step and only minimal training for the operator [3]. NIST describes it as a "swab in, profile out" process that runs the extraction, copying, and reading of the DNA inside a single instrument [3].

That speed changes where DNA testing can happen. A profile can be produced at a police booking station or a mass-casualty scene instead of waiting days or weeks for a lab, which is why rapid DNA is tracked as an active research and standards area [11]. The trade-off is that these instruments work best on clean, single-source samples, so they do not replace a laboratory for the mixed samples a crime scene usually produces.

Next-generation sequencing and forensic genomics

Next-generation sequencing, also called massively parallel sequencing, reads the actual order of DNA letters rather than only measuring the length of repeated segments the way older equipment does. For the standard identification markers, moving to sequencing produces a more discriminating profile and a better ability to separate the individual contributors in a DNA mixture [4].

The gain is largest for difficult samples. When the FBI Laboratory validated a sequencing method for mitochondrial DNA, the kind recovered from hair shafts, bones, and teeth, it reported more than a 20-fold increase in sensitivity over the older Sanger method it replaced [6]. Mitochondrial DNA is passed down the maternal line, so it cannot single out one person, but it can include or exclude a whole lineage when nuclear DNA is too degraded to test [6]. The same sequencing also underpins the SNP work behind genetic genealogy and phenotyping [11].

Predicting appearance with forensic DNA phenotyping

Forensic DNA phenotyping predicts what an unknown person probably looks like from a crime scene sample, for use when there is no database match to identify them directly [5]. Validated tools can estimate eye, hair, and skin color, and research has extended predictions to traits such as freckling, hair loss in men, and taller stature, plus biogeographic ancestry and, more roughly, age [5].

These predictions are investigative leads, not identifications. They narrow a suspect pool or correct a mistaken eyewitness description, and accuracy varies from trait to trait, which is why the National Institute of Justice keeps funding work on it [11]. The techniques A to Z page walks through how these DNA methods sit alongside fingerprints, toxicology, and the rest.

Getting more from trace and touch DNA

Trace DNA, sometimes called touch DNA, is the small number of cells a person leaves on something they handled. It is valuable but hard to work with, because there is so little of it and it is easy to lose during standard processing [7]. One improvement is direct PCR, which adds the swab straight into the copying step and skips the extraction stage where DNA is normally lost, producing a complete profile in under three hours in NIJ-funded testing [7].

How much you can recover also depends on the object and its history. NIJ research found touch DNA degrades fastest under ultraviolet light and in hot, dry conditions, and that a smooth steel surface tends to hold usable DNA better than fabric [8]. For the messy mixtures these samples produce, laboratories increasingly use probabilistic genotyping software to estimate how strongly a given person is or is not part of the mixture [11].

Digital and AI-assisted forensics

Phones, laptops, and cloud accounts are now routine sources of evidence, which raises a practical question: do the tools that pull that data off actually work as claimed? NIST runs the Computer Forensics Tool Testing program, which publishes independent test results for software that images drives, recovers deleted files, and extracts data from mobile devices and cloud services [12].

Machine-learning software is beginning to help investigators triage very large volumes of files and to interpret complex DNA mixtures [11]. These tools are still being validated, and their results are only as trustworthy as the testing behind them, which is the same standard the rest of forensic science is now being held to [12].

The push for validated methods: the 2009 NAS and 2016 PCAST reports

Two reviews reset expectations for the whole field. In 2009 the National Research Council, part of the National Academy of Sciences, reported that much of forensic science lacked the standards and research base to support its courtroom claims, and it called for enforceable standards, mandatory accreditation and certification, and a dedicated federal science body [9].

In 2016 the President's Council of Advisors on Science and Technology went method by method. It found that single-source DNA, DNA mixtures of no more than two people, and latent fingerprint comparison met its bar for "foundational validity," while bite-mark analysis, firearms and toolmark comparison, footwear marks, and microscopic hair comparison did not yet meet it [10]. Those findings still shape which evidence judges admit and how experts are allowed to phrase their conclusions. For a broader tour of how each discipline works, see forensics explained.

Sources

1. National Human Genome Research Institute (NIH), Investigative Genomics
2. J.V. Chamary, How Genetic Genealogy Helped Catch The Golden State Killer, Forbes (June 30, 2020)
3. National Institute of Standards and Technology (NIST), Rapid DNA Typing
4. National Institute of Justice, Forensic DNA Applications of Massively Parallel / Next Generation Sequencing
5. Recent advances in Forensic DNA Phenotyping of appearance, ancestry and age, Forensic Science International: Genetics (2023), PubMed 37084623
6. Validation of NGS for mitochondrial DNA casework at the FBI Laboratory, Forensic Science International: Genetics (2019), PubMed 31629185
7. National Institute of Justice, Improving Analysis of "Trace DNA" Evidence
8. National Institute of Justice, Persistence of Touch DNA for Analysis
9. National Research Council (National Academy of Sciences), Strengthening Forensic Science in the United States: A Path Forward (2009)
10. National Institute of Justice, Post-PCAST Court Decisions Assessing the Admissibility of Forensic Science Evidence (summary of the 2016 PCAST report)
11. National Institute of Justice, Forensic Biology Research and Development at NIJ
12. National Institute of Standards and Technology (NIST), Computer Forensics Tool Testing (CFTT) Program