DDC Forensic Services provides comprehensive services in cases involving DNA evidence, from crime scene to courtroom. Our DNA forensic testing services help identify possible sources of DNA evidence, create DNA profiles from these sources, and compare the profiles of suspect, victim, and evidence. Our forensic scientists can deliver expert testimonies and provide case consultation and review of the DNA evidence presented in a case upon request.
Finding DNA Evidence
From identifying perpetrators through a "cold hit" on the national convicted offender database, CODIS (Combined DNA Index System), to exonerating wrongfully convicted individuals, DNA testing has increasingly become an indispensable tool to help ensure justice.
DDC has a number of presumptive and confirmatory tests that detect the presence of blood, semen, and other biological materials left behind at a crime scene. When sources of human DNA are found, our laboratory scientists will extract the DNA for testing and analysis. Depending on the sample type (blood, hair, bone, vaginal swab, etc.) and condition, one or more of the following testing systems may be used:
STR "Short Tandem Repeat" typing using the 13 core CODIS markers. This is the most commonly used and most powerful of the testing systems. The profile generated is unique to each individual and is regularly used for all types of biological samples. Additional markers for extended testing are available.
Y-chromosome STR typing of 17 markers that are male specific, paternally inherited, and therefore not unique to an individual. Y-STR testing is often used in samples containing a mixture of male and female DNA where the two cannot be separated, as in sexual assault cases.
Mitochondrial DNA sequence analysis is often used in cases where the sample contains degraded DNA or lacks nuclear DNA, such as a hair shaft without the root, or other difficult samples such as bone or teeth. This test system is maternally inherited and therefore is not unique to an individual.
Mini-STR fragment analysis is an alternative approach for testing the eight largest and most difficult loci to amplify. This testing system provides increased ability to obtain results from compromised samples that previously would have yielded unlimited or no genetic data.
DDC offers complimentary training on collecting crime scene evidence for DNA analysis. We conduct trainings at our mock crime scene facility in Fairfield, Ohio. Please contact us for more information.
Linking DNA Evidence
When DNA evidence has been analyzed, the DNA profile can be used to link the evidence to a suspect, or to link different crimes together, such as when DNA from a single perpetrator is found at two different crime scenes.
DNA evidence can also be used to prove the innocence of a falsely accused or wrongly convicted person, as well as identify the bodies of victims of violent crimes, accidents, or natural disasters. The power of DNA technology in identifying individuals and establishing biological relationships makes its applications limitless.