A surgical suture cutter that has a “wishbone” configuration and is provided with a locking mechanism having a mid-point lock that allows two operating handles to be locked in a predetermined position at which point the cutting jaw is held flush with the shaft but suture between the jaws of the cutter is allowed to slide without being cut. The locking mechanism is formed of first and second members provided with a first engagement element (for example, a hook) and a second engagement element (for example, a notch), to allow secure engagement of the first engagement element when the suture cutter instrument is in the mid-point locked position.