Diabetes mellitus type 1 and type 2 are diseases characterized by impaired regulation of blood glucose due to decreased insulin production and insulin resistance, respectively. Management of diabetes mellitus often requires injection of exogenous insulin. Continuous subcutaneous insulin infusion (CSII or insulin pump) is a diabetes treatment modality utilizing a device to aid in regulation of glycemic control. Malfunctions in device components can have rare fatal consequences. Described in this report are six fatalities due to one such malfunction, the failure of plastic cannulas of CSII devices to penetrate the skin and deliver insulin, resulting in fatal diabetic ketoacidosis (DKA). The cases derive from four different death investigation systems. For each case, scene and autopsy findings are presented, as well as selected toxicology and histology findings. These cases illustrate the importance of careful examination of CSII devices in death investigations and introduce a discussion on discrepant manner of death classifications.