Accurate root cause determination of integrated circuit devices necessitates the preservation of evidence during failure analysis. Identifying the cause of systemic defects requires capturing physical evidence provided by very few customer returns. Each piece of physical evidence is valuable due to the scarcity of returns in most cases less than 1 ppm. Harvesting infrequent physical evidence requires that each attempt to decapsulate a fail unit has a high probability of retaining the material that caused the defect. A measured method that retains the critical evidence is the fastest way to solve a defect driven systemic failure mechanism because one gathers the evidence more efficiently. This paper presents two case studies of improved evidence gathering using halogen-free microwave induced plasma (MIP) decapsulation during the root cause investigations. This relatively new method of decapsulation enabled us to preserve evidence, including any changes to the metal and die surface structures along with the presence of contaminants or by-products of failure mechanisms.