A defibrillator (10) having one or more redundant systems (202) each including functionally interchangeable components (204) from which one component is selected for current operation. Manual or automatic selection of one component in each redundant system is made to form an operational defibrillator. Preferably, such selection is based on a real-time evaluation of the operational integrity of all operational components in a redundant system. Such real-time evaluations may be performed by monitoring systems (210) within a controller, by an external test system within or external to the defibrillator or by self-test mechanisms internal to the operational components themselves. Factors such as user preferences, default component assignment, and predetermined arrangements of operational component combinations may be included in the selection determination along with the operational integrity of each operational component. If certain, non-critical components fail with no functionally interchangeable components available, then the redundant system comprising such a failed component is not made operational. The remaining systems of the defibrillator may still be implemented to form a defibrillator sufficient for defibrillation yet lacking the capability to implement the functions allocated to the malfunctioning, degraded or otherwise absent redundant system.