To explore the assessment challenge related to case based learning we study how experienced clinical teachers--i.e., those who regularly teach and assess case-based learning--conceptualize the notion of competent reasoning performance for specific teaching cases. Through an in-depth qualitative case study of five expert teachers, we investigate whether they share a common concept of what constitutes a good reasoning performance for a set of three teaching cases. We ask expert teachers to reflect on their problem-solving performances to extract specific expectations regarding the assessment of learners. Using visual representations of their performance, experts inspect and identify whether key elements are considered critical, necessary, and useful for the assessment of learners' performance. Findings indicate that despite solving cases differently, expert teachers share a common concept regarding the key elements that demonstrate good clinical reasoning for specific cases. These results and methods used to trigger assessment criteria from expert clinical teachers show potential for the development of process measures in the assessment of clinical reasoning.