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DNA - A Prosecutor’s Practice Notebook Inventory

DNA Profiles: Single Source and Mixed (nDNA)

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A DNA profile can be from a single person (single source profile) or from two or more persons (DNA mixture). A DNA profile from two or more persons can be either resolvable (the analyst is able to identify the DNA profile of the major contributor to the mixture) or irresolvable (cannot distinguish between profiles within a mixture). An irresolvable mixture most often occurs when two or more persons contribute relatively equally amounts of DNA to the mixture.  

The significance of a match between a major contributor profile or predominate profile portion of a DNA mixture and the profile from a particular individual (suspect, victim, etc.) is calculated in the same way as the significance for a single source profile. However, the statistical calculation of the significance of an irresolvable DNA mixture cannot be calculated in the same way. The irresolvable mixture will determine the statistical weight calculation applied.

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