A medical syringe for delivering a medicament to a patient, comprising: a syringe assembly comprising a barrel having a forward end and a rear end and defining a reservoir within which a medicament may be contained, and a needle cannula having a forward tip and being coupled to said forward end of said barrel and in fluid communication with said reservoir; a hub provided on said forward end of said barrel; a shield movably mounted on said hub at a first position; an urging member for urging said shield in a forward direction relative to said barrel; and a cover sleeve having a rear end connected to one of said hub and said barrel and a front end, said cover sleeve surrounding a portion of said hub, said shield being movable from said first position to a second position against the urgency of said urging member when said needle cannula is inserted into a patient for delivery of the medicament and said shield being moveable from said second position to a third position by the influence of said urging member upon removal of said needle cannula from said patient, wherein said shield is locked in said third position and said forward tip of said needle cannula is covered by said shield when said shield is in said third position, characterized in that said hub defines a track arrangement having an entry track and a lock-out track, said entry track and said lock-out track being joined at an intersection, and said shield includes a pin arranged on a flexible lever arm, said flexible lever arm having a base end connected to said shield and a free end, said pin being arranged proximate said free end of said flexible lever arm and guidable in said track arrangement during movement of the shield between said first, second, and third positions. a syringe assembly comprising a barrel having a forward end and a rear end and defining a reservoir within which a medicament may be contained, and a needle cannula having a forward tip and being coupled to said forward end of said barrel and in fluid communication with said reservoir; a hub provided on said forward end of said barrel; a shield movably mounted on said hub at a first position; an urging member for urging said shield in a forward direction relative to said barrel; and a cover sleeve having a rear end connected to one of said hub and said barrel and a front end, said cover sleeve surrounding a portion of said hub, said shield being movable from said first position to a second position against the urgency of said urging member when said needle cannula is inserted into a patient for delivery of the medicament and said shield being moveable from said second position to a third position by the influence of said urging member upon removal of said needle cannula from said patient, wherein said shield is locked in said third position and said forward tip of said needle cannula is covered by said shield when said shield is in said third position, characterized in that said hub defines a track arrangement having an entry track and a lock-out track, said entry track and said lock-out track being joined at an intersection, and said shield includes a pin arranged on a flexible lever arm, said flexible lever arm having a base end connected to said shield and a free end, said pin being arranged proximate said free end of said flexible lever arm and guidable in said track arrangement during movement of the shield between said first, second, and third positions.