The invention is an automated core biopsy instrument that may be operated with one hand. The instrument has a single activation element that causes a stylet to advance into the tissue of interest as a cutting cannula disposed around the stylet is fired to shear off the tissue into specimen notches disposed in the stylet. The invention is constructed so that the stylet and cutting cannula may be separately driven and biased. The cocking mechanism of the automated core biopsy instrument is used to cock both the stylet assembly and cutting cannula assemblies against separate biasing springs. Manipulation of the cocking mechanism permits the exposure of tissue in the specimen notches when desired. The instrument has a locking mechanism that is used to prevent inadvertent firing of the automated core biopsy instrument.