In this study, a previously developed optimized workflow for cases with little biological evidence other than touch DNA was tested on aged fingerprints to determine whether improved short tandem repeat (STR) profiles could be obtained.
Due to recent improvements in forensic DNA testing kit sensitivity, there has been an increased demand in the criminal justice community to revisit past convictions or cold cases. Some of these cases have little biological evidence other than touch DNA in the form of archived latent fingerprint lift cards. In the current study, 2-year-old samples processed with the optimized workflow produced an average of approximately five more STR alleles per profile over the traditional method. The optimized workflow also produced detectable alleles in samples aged out to 28 years. Of the methods tested, the optimized workflow resulted in the most informative profiles from evidence samples more representative of the forensic need. This workflow is recommended for use with archived latent fingerprint samples, regardless of the archival time. The use of the optimized workflow on aged archived latent fingerprint (ALFP) lift card samples (aged 2–28 years) improved the number of STR alleles recovered, providing more discriminatory STR profiles than those processed using the traditional workflow. Interpretable STR alleles can be detected from ALFP lift card samples stored as long as 28 years when the optimized procedures are followed. The use of individual laboratory-sterilized tools for sample preparation and the addition of a re-purification step with Centri-Sep columns in the recommended optimized workflow seem to limit the ability to detect low-level secondary DNA sources. (publisher abstract modified)