There are some caveats to this technique. First, being a prolific writer does not necessarily guarantee expertise. Whether or not this makes a writer an expert for the purposes of the search is something only the person wanting to locate the expert can determine. Third, if an author's name pops up frequently, maybe the author is a journalist rather than a practitioner. Again, this does not disqualify the author as an expert.
Many professional journalists are experts.
But if you want to put a food-spoilage expert on the witness stand, a journalist will probably not have the same cachet as a scientist. On the other hand, the journalist may be willing to share sources with you over the phone and direct you to one of the experts in his or her own internal database of experts. Another journalistic and fundraising technique is searching biographical directories. Using fields, you can identify graduates of Ivy League colleges who now live in California or people who received their degree in the 1970s and are now active in local civic groups. The people fields in company directory databases can be used to find individuals meeting certain position criteria.