Marshall's arguments, known as the Marshall hypotheses, are as follows: support for capital punishment is inversely associated with knowledge about it; exposure to information about capital punishment produces sentiments in opposition to capital punishment; and exposure to information about capital punishment will have no impact on those who support it for retributive reasons. The subjects for this study were 70 undergraduate students of a large, urban university in west-central Florida. They were enrolled in a special topics course on the death penalty within a criminology major during the summer of 2003. The course met for 3.5 hours a day twice a week for 6 weeks. The assigned text for the course was Bohm's "Deathquest II" (2003b). In addition to the text, other sources of death penalty information were also supplied to students. Students' attitudes toward capital punishment were assessed before and after the course. The study measured knowledge gain and its association with attitudinal change regarding the death penalty. The study found some evidence that death-penalty attitudes and beliefs were inversely linked with a student's level of knowledge about how the death penalty is used and its impact. Death-penalty supporters were somewhat less informed than death-penalty opponents. Exposure to death penalty information and knowledge gains tended to be associated with attitudinal change in directions suggested by Marshall' hypotheses; however, retributivists' attitudes toward and beliefs about capital punishment were not any more resistant to change than were the attitudes or beliefs of non-retributivists, thus failing to support Marshall's third hypothesis. 6 tables and 26 references