A system for use during administration of cardiopulmonary resuscitation (CPR) chest compressions on a victim is described. The system includes a chest compression monitor that includes a motion sensor configured to generate signals indicative of the victim's chest motion and a control system communicatively coupled to the chest compression monitor and configured to receive the generated signals, detect compression waveform features representative of the chest compressions based on the received signals, compare the features to a pre-determined criterion that distinguishes between a manual source of the chest compressions and a piston-based chest compression device source, determine whether the source of the chest compressions is the manual or the piston-based chest compression device source based on the comparison, and generate an output based on whether the source of the chest compressions is determined to be the manual or the piston-based chest compression device source.