The present technology describes various embodiments of systems and methods for analyzing electrocardiograms to detect ventricular fibrillation. In several embodiments, systems for detecting ventricular fibrillation can be implemented without interrupting cardiopulmonary resuscitation. In one embodiment, a method of identifying a cardiac rhythm in a person includes recording an electrocardiogram signal of the person and stratifying the signal. A signal having a parameter value within a pre-determined range is categorized as a shockable ventricular fibrillation signal while a signal having a parameter value outside the pre-determined range is categorized as a non-shockable signal.