By Cairenn Binder, Coast to Coast Genetic Genealogy Services

It is critical for investigative genetic genealogy (IGG) practitioners to work in partnership with experts in forensic DNA to ensure that valuable DNA evidence is not squandered in pursuit of a profile for IGG. At times, although it is disappointing, this may mean that the best thing to do is turn down a case.

Recently our team was approached by an agency wishing to identify the perpetrator in a violent crime. The DNA evidence thought to be from the perpetrator was mixed with DNA from the victim, and the quantity of perpetrator DNA was exceedingly small.

We consulted (4) four of our partner laboratories to determine the best path forward to develop a SNP profile for the individual. It was determined by all four that the quantity of perpetrator DNA was too little to pursue genotyping with microarray analysis, which has been successfully used to deconvolute mixtures where one profile is known.

Additionally, while the use of whole genome sequencing (WGS) could potentially be used to develop a profile given the small quantity of perpetrator DNA available, deconvolution of mixed profiles using WGS is in its infancy and cannot reliably be depended upon. One expert stated, “I would be wary of any lab that says they have this capability, especially from low quantity/quality samples.”

Our conclusion after consultation with experts in the field was to advise the agency investigating this case to wait… for now. Our team provided a rationale for our recommendations as well as contact information for each of the laboratories we consulted.

We are living in a lively period in which many laboratories are working in tandem to develop and advance methods for DNA analysis using SNP profiling, including deconvolution of mixed specimens. It is our hope that in time, this case will become eligible for genotyping with WGS after technology improves and further study determines it can reliably be used in mixed samples.

This case in particular highlights the necessity of partnership and collaboration with forensic DNA specialists. As IGG practitioners we rely on guidance from our laboratory partners who are experts in the field, and adhering to their recommendations is of paramount importance in ultimately securing justice for victims of violent crime.