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Principles of Forensic DNA for Officers of the Court

Statistical Calculations and Source Attribution

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Once an individual's 20-locus STR profile is identified, it is statistically improbable that anyone else in the world will have the same profile, unless that person has an identical twin. Identical twins (twins derived from a single fertilized egg) have identical STR DNA profiles.

Based on individual laboratory policy, the report may include a statement of source attribution in addition to, or in place of, a statistical estimate.

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