BOONE—An actor’s quest to learn about his ancestors took him to La Coruña, a port city in northern Spain, where Dr. Edward Behrend-Martinez’s expertise in Spanish trials helped provide the dramatic conclusion in the television program “Who Do You Think You Are?”

Behrend-Martinez is an associate professor and assistant chair in Appalachian State University’s Department of History.

The series follows celebrities – from sport figures and actors to musicians – who visit archives, libraries and other sites as they trace their family tree as far as records allow, all with the help of historians. The season opener, which aired Feb. 3 and is available on the program’s website, www.nbc.com/who-do-you-think-you-are, featured actor Martin Sheen who learns details about his Irish-Spanish heritage.

Behrend-Martinez had never watched the television program before being called by producers to provide historic insight regarding a trial that Sheen’s great-great-great-great-grandfather presided over....