Efficacy of Prayer: A Critical Examination of Claims Irwin Tessman, Jack Tessman From: Volume 24, No. 2 March / April 2000 ShareTweet Irwin Tessman Irwin Tessman is a professor emeritus of biology at Purdue University. His primary scientific research is on DNA damage, repair, and mutation. He has written critically about alternative medicine and intercessory prayer. See more articles This article is available to subscribers only. Subscribe now or log in to read this article.