Introducing Forensic Genomics

For the first time in decades, we are witnessing a revolution in forensic DNA testing that promises to bring closure to the tragic number of cold cases currently stalled at some point in the investigative process. There are hundreds of thousands of cold cases in the United States alone. The National Institute of Justice calls it a silent mass disaster. Cold cases in the United States and worldwide continue to accumulate, the vast majority of which will not be solved using traditional forensic DNA testing frameworks. One such framework is the Combined DNA Index System (CODIS), a Federal Bureau of Investigation program that supports DNA databases and infrastructure for using these databases to search unknown DNAs against a catalog of known felons. While CODIS will remain a critical and irreplaceable component of forensic DNA testing in the foreseeable future, countless solvable cases remain unsolved due to the simple fact that CODIS was designed from the start—when DNA testing was in its infancy—to identify those individuals who had already been identified by other methods. While effective in tracking repeat crime by convicted criminals, CODIS is ineffective for cases such as unidentified remains, as many of them are victims and not criminals. Of course, CODIS will not reveal the identification of all criminals either. Many perpetrators of crimes have yet to have be caught, and even those who are caught (and even convicted) can accidently be missing from CODIS. In the past few years, incredible advances in forensic genetic testing have transformed what forensic professionals can learn from DNA left at crime scenes. A growing number of seemingly ‘‘unsolvable’’ cases are now being closed—most notably the capture of the Golden State Killer in April 2018. Testing was pivotal in finding the killer and ensuring his life sentence, delivered in August 2020. These newer DNA testing methods, of which there are many, rely on ‘‘reading’’ tens to hundreds of thousands of DNA markers across the genome. In comparison, a full DNA profile for CODIS contains just 20 core markers— or 20 sites on the human genome. When a CODIS profile is entered into CODIS, a match can be made to someone already in the database. In some states, CODIS can be used to search immediate family relationships, such as parent–offspring, with a technique called ‘‘familial DNA testing.’’ However, to detect the sorts of distant genetic relationships used to catch the Golden State Killer, a much richer genomic profile is needed, comprising as many as hundreds of thousands of DNA markers. Measuring these markers requires new methods typically unavailable at laboratories that offer conventional CODIS testing. The foundation for these new methods comes from consumer, research, and medical DNA testing applications over the past decade. As this cutting-edge technology is new for most criminal investigations, there are not many resources available to guide investigators and forensic professionals through the process. What cold cases are best for these advanced forms of DNA testing? What are the considerations, trade-offs, and risks? Which scientific methods should be used for which applications? Most importantly, how do you return the most value to forensic professionals while consuming the least amount of evidence and budget?