Final answer:
Hair specimens with the root or follicle attached are the richest source of nuclear DNA due to the presence of living cells containing genetic information.
Step-by-step explanation:
The types of hair specimens that are potentially the richest source of nuclear DNA are those that contain the hair root or follicle. This is because the root contains living cells from which nuclear DNA, with all the individual's genetic information, can be extracted. Hair that is naturally shed or pulled out with the follicle attached is typically used in DNA analysis because it retains this cellular material with the nuclear DNA intact. Conversely, cut hair strands do not contain the follicle and are therefore considerably less useful for nuclear DNA extraction.