Reference Population Database
Definition
A curated collection of allele frequencies or feature measurements from a defined population, used to estimate the probability that a randomly chosen member of that population would show the same forensic feature as the questioned sample.
- Content
- Allele frequencies or feature measurements from a defined population
- Purpose
- Estimating random-match probability for a forensic feature
- Dependency
- Must match the relevant population for the case
Common questions
Why can a match statistic differ between two forensic laboratories examining the same evidence?+
Laboratories may draw on different reference population databases, for example national versus regional allele frequency sets, and the underlying sample sizes and compositions differ, so the calculated probability can vary even though the underlying match is identical.
How is a reference population database kept current?+
Frequencies are periodically re-sampled and revalidated as population demographics shift and as sampling coverage improves, since a stale or unrepresentative database can misstate rarity for the population actually relevant to a case.
Related terms
- Allele Frequency
- The proportion of a specific allele variant at a given genetic locus in a defined population. Forensic match probability calculations multiply the...
- Hardy-Weinberg Equilibrium (HWE)
- The expected genotype frequency in a large, randomly mating population with no selection, mutation, or migration. Under HWE, the frequency of a...
- Minimum Allele Frequency (Minimum Frequency Ceiling)
- A conservative lower bound applied when an allele is absent or very rare in the database, to prevent an artificially inflated match...
- Population Substructure
- The condition in which allele frequencies differ systematically between subgroups within a nominally single population. Substructure means that individuals within a subgroup...
- Theta Correction (FST or Coancestry Coefficient)
- A statistical adjustment applied to DNA match probability calculations to account for expected allele-sharing within subpopulations due to substructure. A theta value...