After twenty-one years in a newsroom, Witham now writes and edits books full time. He is the author of fourteen books. In 2007 he served as editor of the bimonthly magazine Science & Spirit. As a former reporter with The Washington Times, Witham wrote more than four thousand news stories, features, and book reviews and has filed stories from Asia, Africa, Europe, the Soviet Union and Latin America. A native of Los Altos, California (born June 1952), Witham earned a bachelor's degree in fine arts from San Jose State University (1974). He and his wife, Kazui Yamamoto, live in Maryland.

Witham has received several national awards for his articles on religion and society, including from the Religion Communicators Council, the Religion Newswriters Association, the D.C. Chapter of the Society of Professional Journalists, and the Templeton Foundation. His book on the American clergy, Who Shall Lead Them?, was named Best Book for 2006 by the Academy of Parish Clergy and the Catholic Press Association named his Curran v. Catholic University a best general interest book.

Witham has written for a number of publications, ranging from Christian Century, the Nation and Beliefnet to Nature and Scientific American. He has spoken before the American Academy of Religion, the American Association for the Advancement of Science, National Association of Evangelicals, the Society of Secular Humanists, the Sunstone Association (Mormon scholars), the Southern Book Festival, the Edinburgh Book Festival, the Cambridge Forum, at the Washington National Cathedral, and has appeared on C-SPAN, Fox News, public television, the "700 Club" and dozens of radio programs including affiliates of National Public Radio.