January 20, 2015
In the world of primetime crime dramas like Law and Order and CSI, it is common knowledge that DNA evidence can help solve crimes and exonerate the innocent. But less understood is the technology used by the forensic genomics community to examine DNA. Cydne Holt, Ph.D., a former director of the San Francisco City and County Forensic Services Division and currently Illumina’s Senior Market Manager for Forensic Genomics, explains how Illumina’s next-generation sequencing technology can help forensic laboratories improve the efficiency and economics of their work.
How is DNA analyzed in forensic laboratories today?
Today, biological samples of unknown origin are routinely collected from crime scenes, sexual assault survivors, and suspicious scenarios. When investigating agencies determine that DNA analysis may be of merit, the samples are sent to a forensic laboratory where DNA is extracted and a PCR-based analysis is performed. This analysis typically examines 13 to 25 locations of the genome, and samples are processed on a capillary electrophoresis instrument one at a time. Biological samples containing mixtures of DNA from two or more individuals can be difficult to understand and interpret because the data generated is based on the size of DNA pieces, not on the actual DNA sequence.
What are the expected improvements with next-generation sequencing, and in particular, Illumina’s new MiSeq FGx Forensic Genomics System?
Although the methods most commonly used in forensic laboratories today are reliable, they are inefficient and do not provide as much information as they could to solve difficult cases. Our solution can help laboratories go from sample to answer with one workflow.
The workflow begins with the ForenSeq DNA Signature Prep Kit, which simultaneous amplifies Combined DNA Index System (CODIS) compatible short-tandem repeats (STRs) and single nucleotide polymorphisms (SNPs). Laboratories gather all the information they need in a single reaction, which is critical in situations where limited DNA is available to test, such as with degraded DNA samples (<120 bp).
Next, using the MiSeq FGx Instrument, which leverages proven Illumina sequencing by synthesis chemistry, laboratories can run their DNA samples 96 at a time. From each sample, they can obtain more than 200 pieces of information about both STRs and SNPs, enabling them to develop more complete DNA profiles based on DNA sequence.
Finally, ForenSeq Universal Analysis Software lessens the burden of data analysis and interpretation on forensic laboratories, particularly from mixed biological samples. Using the software, laboratories can provide law enforcement with more complete profiles, enabling analysts to spend more time on other duties important to increasing public safety and decreasing crime.
How do cases with DNA evidence go cold? Can forensic tools developed by Illumina help?
Even when a forensic laboratory is able to create a “complete DNA profile” based on a DNA sample (which can be difficult when DNA samples are highly degraded), cases often reach dead ends. This happens when the DNA profile query does not hit any profile in the CODIS database and there is no suspect in the case. With information about the visible traits of the person whose DNA is contained in the biological sample, such as hair color, eye color, as well as bio-geographical ancestry, laboratories can provide police with additional information needed to identify suspects, exonerate the innocent, and ultimately solve cases that would otherwise go cold.
As more information about the genetic basis for physical characteristics is uncovered in the future, the MiSeq FGx Forensic Genomics System will also be able to integrate markers that are indicative of traits such as skin tone, facial morphology, hair texture, height, weight, and age of the DNA contributor.
Besides solving crimes, how else can the MiSeq FGx Forensic Genomics System be used?
In addition to crime solving, the MiSeq FGx Forensic Genomics System can be used in the identification of human remains from mass disasters such as airline crashes or terrorism cases where the deceased may otherwise be unrecognizable. The System allows labs to use targeted sequencing on low-level samples (<1ng), including those that are partially degraded, to produce high-resolution identification. It can also be used to help identify unidentified or decomposed human remains, found without other identifying characteristics.