7. A method for biometric indexing and searching based on a matching operation, for a probe in a biometric corpus comprising: performing the matching operation between templates in the biometric corpus and prototype templates to obtain template-match scores; averaging the template-match scores for each of a plurality of templates to generate a template-typicality score; and dividing template-typicality scores of all the templates in the biometric corpus into typicality ranges, each typicality range corresponding to a typicality sub-corpus of a typicality-indexed corpus that has about a same number of templates as other typicality sub-corpuses corresponding to other typicality ranges, and each of templates in the typicality sub-corpus having a template-typicality score within a typicality range of the typicality sub-corpus.
8. The method of claim 7 further comprising: performing the matching operation between the probe and the prototype templates to generate probe-match scores; averaging the probe-match scores to generate a probe-typicality score; and selecting a typicality sub-corpus based on the probe-typicality score as the search corpus.