A hand-actuated injector (10) includes a handle assembly (200) for providing discharge and aspiration strokes for a plunger (108). The handle assembly (200) includes first and second scissor-like handle members (204, 212) that provide a discharge stroke for the plunger (108) when manipulated in a first manner, and an aspiration stroke for the plunger (108) when manipulated in an opposite, second manner. The handle assembly (200) also includes a meshed-gear locking mechanism or hinge (248) that selectively prevents or at least limits relative movement between the first and second handle members (204, 212) in a manner that is associated with providing an aspiration stroke for the plunger (108).
