Identification of Forensic Samples by Using an Infrared-based Automatic DNA Sequencer

We have recently introduced a new protocol for analyzing all core loci of the Federal Bureau of Investigation’s (FBI) CombinedDNAIndex System (CODIS) with an infrared (IR) automaticDNAsequencer (LI-COR 4200). The amplicons were labeled with forward oligonucleotide primers, covalently linked to a new infrared fluorescent molecule (IRDye™800). The alleleswere displayed as familiar autoradiogram-like images with real-time detection. This protocol was employed for paternity testing, population studies, and identification of degraded forensic samples. We extensively analyzed some simulated forensic samples andmixed stains (blood, semen, saliva, bones, and fixed archival embedded tissues), comparing the results with donor samples. Sensitivity studies were also performed for the four multiplex systems. Our results show the efficiency, reliability, and accuracy of the IR system for the analysis of forensic samples. We also compared the efficiency of the multiplex protocol with ultraviolet (UV) technology. Paternity tests, undegraded DNA samples, and real forensic samples were analyzed with this approach based on IR technology and with UV-based automatic sequencers in combination with commercially-available kits. The comparability of the results with thewidespreadUVmethods suggests that it is possible to exchange data between laboratories using the same core group of markers but different primer sets and detection methods.