n.an appraisal technique in which a portion within a body of records is chosen for permanent retention based on its unusual qualities or greater historical importanceCook 1991b, 41Exceptional selection focuses on special cases within the case file series worthy of archival retention. If the series as a whole does not have any collective value as outlined in the previous two sections, then this final step takes place by itself. If the series as a whole does have collective value, that must be determined first, before the search for outstanding individual files or items within a series commences.Hockey 2000I should probably add that the archival institutions which were using sampling also retained all files before a grandparent date. This date often related to the introduction of an electronic database containing summary details on each offender. This provides a measure of comfort to future genealogical researchers—there should be some kind of record of their ancestor's time in jail, even if it is only an electronic summary record. If their ancestor did commit a “major” crime, then their file should also be retained under the kind of “exceptional selection” approach outlined above.National Archives 2005, 6–7Exceptional Selection / Suitable for: Mostly homogenous file series with a few interesting cases. / Example: Death duties where files concerning persons of note are deemed worthy of preservation.
Exceptional selection includes such appraisal decisions as deciding to preserve court case files relating to the most notorious crimes (murder and rape) or the records of the famous and infamous over those of others. The idea behind exceptional selection is that the archivist chooses those files most likely to be used in the future. In some cases, exceptional selection is also a type of oversampling, although exceptional selection may also be the only sampling technique used for a body of records.