Validation of a Confirmatory Proteomic Mass Spectrometry Body Fluid Assay for Use in Publicly Funded Forensic Laboratories

Abstract

DNA STR identity testing has become foundational to forensic investigations.  It is scientifically sound, statistically rigorous and above all confirmatory.  Yet as this technology becomes increasingly more sensitive - able to identify an individual from only a few cells - the need to know the source of an individual’s DNA profile (blood, saliva or semen) is becoming more important.  For example, the caretaker of a toddler or incapacitated patient accused of sexual assault could justifiably claim that their DNA profile would be expected on a victim they bathe, toilet and dress, and their profile is from shedding skin, direct, or even secondary skin cell transfer.  These same arguments could be made in numerous forensic investigations, e.g. date rape or homicides when the victim and suspect know each other.  Knowing that a profile came from semen gives context to a case that goes beyond DNA STR identification.  Prosecutors have begun to push back against forensic laboratories that have eliminated serology testing, stating that the source of DNA is important to the outcome of their cases (see letter of support from the Manhattan District Attorney’s Office Appendix 2).  However, current serology methods, with the exception of microscopic identification of sperm, are presumptive, and do not carry the scientific weight, and therefore evidentiary significance, of confirmatory tests.  To address this issue, i.e. establish a confirmatory body fluid assay, NIJ has spent >$13 million dollars over the past 14 years on more than thirty research grants (Appendix 3) aimed at identifying a method that can be used on a routine basis in any forensic laboratory.  We, the NYC OCME, have received two such basic research grants and have developed a confirmatory body fluid assay ready for validation and introduction into routine casework, not just here, but at any forensic laboratory throughout the nation.  Indeed, in cooperation with NIJ’s Forensic Laboratory Needs Technical Working Group (FLN-TWG) we published a technical white paper this year (Implementation Strategies: Proteomic Mass Spectrometry for Biology Fluid Identification, Appendix 4) to aid other laboratories establish this test in their labs.  Here we propose to perform a thorough and statistically rigorous validation (as per NIJ guidelines, Appendix 5) of our assay.  Results will be shared with other forensic laboratories, and published in a peer reviewed journal - as that will be required for the inevitable Frye/Daubert hearings that accompany the introduction of new techniques in the judicial system.