Well constructed sub-population databases are fundamental to the application of DNA-based forensic statistics. The size of such databases can affect the ability to examine adequately statistical or population genetic features, and the integrity of both the DNA profile and associated ethnicity information is also of importance. Use of short tandem repeat (STR) DNA profiling technology and the thoughtful construction of the governing legislation has seen large databases of DNA profiles collated for the four major sub-populations of New Zealand. Examination of the data illustrates the suitability of self-declaration as a means of categorizing samples on the basis of ethnicity.