Current state-of-the-art AEDs provide for no alternative other than to stop precordial compression to identify the victim's heart rhythm during the CPR. Yet interruptions of compression for as little as 10 seconds compromise outcomes. Accordingly, the capability of identifying shockable or non-shockable rhythm without interrupting precordial compression is intended. Such has been accomplished with an identifier algorithm (QRSID) which utilizes wavelet decomposition for identification of either the pressure of a QRS or its absence, compatible with VF rhythms even when corrupted by precordial compression artifacts. We have achieved a specificity of 0.95 and a sensitivity of 0.92 in experimental studies.