The Australian Federal Police (AFP) National DNA Program for Unidentified and Missing Persons recently utilized advanced DNA technology to solve a 40-year-old missing persons case in South Australia. The case involved skeletal remains found on Kangaroo Island in 1983, and it wasn’t until June 2023 that the remains were identified as William Hardie through advances in forensic genomics and genealogy.
The AFP DNA program used similar technology to direct-to-consumer DNA testing companies like AncestryDNA and 23andMe. These companies offer DNA-based exploration of ancestral origins through saliva samples. But how does this technology help solve cold cases?
Humans share more than 99% of their DNA, with the remaining 1% containing genetic differences that provide clues about ancestry and other traits. Consumer DNA testing companies use microarrays to analyze this non-identical DNA, targeting up to a million genetic variants called single nucleotide polymorphisms (SNPs). By comparing these SNPs, it is possible to identify relatives and trace ancestral connections over multiple generations.
However, identifying human remains using ancestral DNA presents unique challenges for forensic scientists, especially in long-term missing persons cases where only skeletal remains are found. DNA extraction from bones or teeth is necessary, but the DNA in these hard tissues degrades over time and exposure to adverse environmental conditions. This often results in insufficient quantity and quality of DNA for analysis.
To overcome these challenges, the AFP DNA program validated a forensic DNA kit that employs targeted sequencing of about 10,000 SNPs. While this method doesn’t analyze as much DNA as microarrays or whole genome sequencing, it is sufficient to link genetic relatives up to the fifth degree, such as second cousins or great-great-great grandparents.
Once a SNP profile is obtained from the remains, it is uploaded to public databases like GEDmatch PRO and FamilyTreeDNA for comparison with profiles of individuals who have volunteered their DNA. If suitable genetic matches are found, genetic genealogists use public information to build family trees and identify common ancestors. They then research relevant family lines to find closer living relatives of the unknown individual.
This process, known as forensic investigative genetic genealogy, has been successful in the United States and is now being utilized in Australia. The AFP DNA program has already resolved 46 cases, including the identification of 15 missing Australians.
To assist in identifying missing persons, individuals can report them missing to the police and provide relevant information for forensic investigation. They can also provide a reference DNA sample by swabbing the inside of their cheek, which will be uploaded to Australia’s national DNA database for comparison with DNA profiles from unknown deceased persons.
Those who have taken consumer DNA tests can also potentially help identify missing people by downloading their DNA data file and uploading it to databases like GEDmatch. By opting in to “law enforcement matching,” individuals consent to their DNA being used by police worldwide to identify human remains and solve violent crimes. Even those who opt out can still contribute to resolving unidentified and missing persons cases through the AFP DNA program.
Without the leads from distant genetic relatives who had previously opted in to this type of DNA matching, the identification of William Hardie’s remains would not have been possible after more than 40 years.