Main findings revealed that justices’ opinions in four major capital punishment cases--Furman v. Georgia (1972), Woodson v. North Carolina (1976), Gregg v. Georgia (1976), and McCleskey v. Kemp (1987)--were clearly contradictory to opinions issued in earlier cases (Type I inconsistency). Moreover, some of the justices’ opinions were contradictory to statements made in written opinions in earlier cases (Type II inconsistency) and in some cases the Court ruled in ways that violated precedents or rules of law (Type III inconsistency). Seven factors are identified as the main explanations for these inconsistencies: (1) Constitutional ambiguity; (2) ideology/attitudes and political affiliation of justices; (3) approach to interpreting the Constitution; (4) strategic rationality and bargaining; (5) changing justices over time; (6) evolving human standards; and (7) public opinion and State legislative activity. The authors argue that the analysis of the four most significant Supreme Court capital punishment cases illustrates that the Supreme Court is unable to provide a clear interpretation of some sections of the Constitution and highlights the disagreement among the justices themselves. Data were drawn from the Supreme Court decisions in four major capital punishment cases. Three main types of inconsistencies in judge’s opinions were examined: (1) issuing an opinion that was contradictory to opinions issued in earlier cases; (2) issuing an opinion that appeared to be contradictory to statements made in written opinions in earlier cases; and (3) ruling in a way that appeared to violate a precedent or rule of law. The analysis also focused on factors that could explain these inconsistencies and changes in opinions across time. Tables, cases cited, references