Rev. Herrin has degrees in American History from Washington and Lee University and Vanderbilt University. He taught High School social studies and coached debate for three years before attending Reformed Theological Seminary in Jackson, Mississippi. During seminary, he began preaching regularly at First Presbyterian Church of Port Gibson, which called him to be its Pastor in 1997. Beginning in October of 2009, he has also supplied the pulpit of the Yokena Presbyterian Church.

From the Fall of 1997 until the Spring of 2014, he taught Bible and Social Studies courses at Chamberlain-Hunt Academy, and served as the school Chaplain. He was a member of the Presbytery of Mississippi (PCUSA) from 1997 until 2012, serving as its Moderator and Stated Clerk during that time. With the formation of the new Presbytery of the Gulf South (EPC) in October of 2014, he began serving as its Stated Clerk.