Richard Otte is a philosopher of religion at the University of California, Santa Cruz. His work is characterized by applying the probability calculus to issues surrounding the rationality of belief in God. One can find links to many of his papers here.
Otte had an exchange with Plantinga on the latter's famous Free Will Defense (FWD) in a recent issue of Philosophy and Phenomenological Research. In Otte's paper, he shows that Plantinga's definition of transworld depravity (TWD) is necessarily false(!). However, Otte goes on to offer an alternative notion that plays a similar role in Plantinga's FWD. Interestingly, Plantinga agrees with Otte's points.
Below are links to the papers:
Otte, Richard. "Transworld Depravity and Unobtainable Worlds", Philosophy and Phenomenological Research 78:1, pp. 165-177.
Plantinga, Alvin. "Transworld Depravity, Transworld Sanctity, and Uncooperative Essences", Philosophy and Phenomenological Research 78:1, pp. 178-191.