Employing authentic cases experienced by practitioners in educational contexts is critical to expanding students' experience and engaging students in authentic problems to promote their real-world problem-solving skills. Although in real life, practitioners experience both success and failure and learn from both, little research has been done so far to conceptualize why and how failure should be employed in case-based learning (CBL) as a way to develop students' abilities to solve ill-structured problems. The goal of this paper is to theoretically justify the need for integrating failure cases in CBL to help students become better problem solvers. To achieve this, this paper attempted to approach failure from the perspective of human error and proposed a classification of failure based on the degree of explicitness of human error involved in problem solving. Based on discussions of potential benefits and challenges of integrating different types of failure cases in education, this paper also proposed instructional design strategies that can help facilitate better use of failure cases.