Forensic DNA Evidence at a Crime Scene: An Investigator's Commentary

The purpose of this article is twofold. The first is to present a law enforcement perspective of the importance of a crime scene, the value of probative evidence, and how to properly recognize, document, and collect evidence. The second purpose is to provide forensic scientists who primarily work in laboratories with the ability to gain insight on how law enforcement personnel process a crime scene. With all the technological advances in the various disciplines associated with forensic science, none have been more spectacular than those in the field of DNA. The development of sophisticated and sensitive instrumentation has led forensic scientists to be able to detect DNA profiles from minute samples of evidence in a much timelier manner. In forensic laboratories, safeguards and protocols associated with ASCLD/LAB International, Forensic Quality Services, and or ISO/IEC 17020:1998 accreditation have been established and implemented to ensure proper case analysis. But no scientist, no instrumentation, and no laboratory could come to a successful conclusion about evidence if that evidence had been compromised or simply missed at a crime scene. Evidence collectors must be trained thoroughly to process a scene and to be able to distinguish between probative evidence and non probative evidence. I am a firm believer of the phrase "garbage in is garbage out." One of the evidence collector's main goals is not only to recover enough DNA so that an eligible CODIS profile can be generated to identify an offender but also, more importantly, to recover sufficient DNA to exonerate the innocent.