A needle-based medical device including a needle shield assembly and a method for constructing the same are disclosed. The needle shield assembly may be deployed such that the device shields the needle passively on removal. A needle shield assembly includes a shield including a restraint member at a proximal end for engagement by an actuator in a non-shielding position. The needle shield assembly includes a shield having a stepped end cap at its distal end a carrier positioned at the distal end of the shield that supports a needle blocking object abutting a first step of the end cap in the non-shielding position and a biasing member within the shield for applying an axial force to the shield. Movement of the actuator disengages the restraint member such that the shield moves, by exertion of the biasing member, from the non-shielding position to a shielding position.
