Attribution theory explains human behavior as a product of either dispositional (internal characteristics of the offender) or situational (environmental or outside factors) attribution styles of respondents. Attribution theory proposes that people who tend to support a dispositional attribution style are more punitive in their philosophies of punishment, so they are more likely to support the death penalty as a form of punishment. Conversely, those who tend to support a situational attribution style are more inclined to support efforts to treat or rehabilitate criminal offenders; thus, they are likely to oppose capital punishment. In testing this theory, the current study obtained data from jury-pool surveys administered during the winter of 2000 in Hillsborough County, FL. A total of 697 questionnaires were usable. The demographic characteristics of the respondents were similar to those of the overall community, except that the respondents had higher average incomes and were more highly educated. Vignettes were used to obtain respondents' death-penalty decisions under various crime scenarios and offender characteristics, including being a juvenile, mentally ill, or mentally retarded. In addition to the vignettes, the questionnaire also contained a series of measures of support for the death penalty that are more common in the research literature. The findings indicate that the respondents with dispositional attribution styles were significantly more likely to recommend a death sentence than were those with situational attribution styles. Moreover, the study found that the effects of a large number of the known correlates of support for the death penalty were fully or substantially mediated by attribution theory measures. The substantive, theoretical, methodological, and legal/policy implications of these findings are discussed. 4 tables, 74 references, and appended factorial survey vignettes