This exercise can be used to stimulate the investigative nature of learners as they use forensic plant pathology techniques to prove the learners' innocence in a mock murder investigation. Learners examine the cleistothecia of plant leaves infected with powdery mildew disease with a compound microscope to identify the type of appendages present. The fungi are identified to genus using the appendage type and the number of asci (spore-containing sacs) inside each cleistothecium using both a written and an illustrated key. Learners compare their samples to the evidence found at the scene of the crime to prove their own innocence. Note: This lab works best in regions that experience cold weather for part of the year.