An extravascular implantable cardioverter-defibrillator system comprising: an implantable electrical stimulation lead including a plurality of electrodes (18, 20, 22) configured to sense cardiac electrical signals from an extravascular location within a patient; an ICD coupled to the implantable electrical stimulation lead, the ICD comprising: a housing that is formed at least partially of a conductive material to serve as a housing electrode; sensing circuitry located within the housing and configured to obtain a first cardiac signal from a first electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode and obtain a second cardiac signal on a second electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode, the second electrode vector having at least one electrode different than the first electrode vector, wherein the second cardiac signal is obtained concurrently with the first cardiac signal; a processor configured to identify beats within the first cardiac signal and the second cardiac signal, apply beat qualification criteria to the beats within the first cardiac signal and the second cardiac signal to determine whether each of the beats is a qualified beat, and generate a beat template based on at least a portion of the beats determined to be qualified beats. an implantable electrical stimulation lead including a plurality of electrodes (18, 20, 22) configured to sense cardiac electrical signals from an extravascular location within a patient; an ICD coupled to the implantable electrical stimulation lead, the ICD comprising: a housing that is formed at least partially of a conductive material to serve as a housing electrode; sensing circuitry located within the housing and configured to obtain a first cardiac signal from a first electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode and obtain a second cardiac signal on a second electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode, the second electrode vector having at least one electrode different than the first electrode vector, wherein the second cardiac signal is obtained concurrently with the first cardiac signal; a processor configured to identify beats within the first cardiac signal and the second cardiac signal, apply beat qualification criteria to the beats within the first cardiac signal and the second cardiac signal to determine whether each of the beats is a qualified beat, and generate a beat template based on at least a portion of the beats determined to be qualified beats. a housing that is formed at least partially of a conductive material to serve as a housing electrode; sensing circuitry located within the housing and configured to obtain a first cardiac signal from a first electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode and obtain a second cardiac signal on a second electrode vector formed via any combination of the plurality of electrodes of the electrical stimulation lead and the housing electrode, the second electrode vector having at least one electrode different than the first electrode vector, wherein the second cardiac signal is obtained concurrently with the first cardiac signal; a processor configured to identify beats within the first cardiac signal and the second cardiac signal, apply beat qualification criteria to the beats within the first cardiac signal and the second cardiac signal to determine whether each of the beats is a qualified beat, and generate a beat template based on at least a portion of the beats determined to be qualified beats.