A needle assembly, comprising: a housing having a proximal end and a distal end, the housing comprising a flash chamber and a specimen collection container holder, the specimen collection container holder including a proximal end, a distal end, and a first tubular sidewall extending therebetween and a second tubular sidewall circumferentially disposed about the first tubular sidewall, a cannula having a patient end, a non-patient end, and a sidewall extending therebetween defining a cannula interior, the patient end of the cannula projecting at least partially from the distal end of the housing, the cannula interior in fluid communication with the flash chamber; and a shield, at least a portion of the shield restrainably engaged between the first tubular sidewall and the second tubular sidewall of the specimen collection holder, the shield axially transitionable over the patient end of the cannula from a retracted position in which the patient end is exposed, to an extended position in which the patient end is shielded by at least a portion of the shield, wherein at least a portion of the flash chamber is visible in the retracted position, wherein at least one of the distal end of the housing and a proximal end of the shield comprises a barrier mechanism engageable with the other of the distal end of the housing and the proximal end of the shield wherein at least a portion of the barrier mechanism is associated with the shield and includes a break that is located external to the housing when the shield is in the extended position for cooperating with a portion of the housing to prevent transition of the shield from the extended position to the retracted position and wherein the barrier mechanism further includes an inwardly directed restraint associated with the distal end of the housing and wherein the restraint is adjacent to the break when the shield is in the extended position for preventing transition of the shield from the extended position to the retracted position. a housing having a proximal end and a distal end, the housing comprising a flash chamber and a specimen collection container holder, the specimen collection container holder including a proximal end, a distal end, and a first tubular sidewall extending therebetween and a second tubular sidewall circumferentially disposed about the first tubular sidewall, a cannula having a patient end, a non-patient end, and a sidewall extending therebetween defining a cannula interior, the patient end of the cannula projecting at least partially from the distal end of the housing, the cannula interior in fluid communication with the flash chamber; and a shield, at least a portion of the shield restrainably engaged between the first tubular sidewall and the second tubular sidewall of the specimen collection holder, the shield axially transitionable over the patient end of the cannula from a retracted position in which the patient end is exposed, to an extended position in which the patient end is shielded by at least a portion of the shield, wherein at least a portion of the flash chamber is visible in the retracted position, wherein at least one of the distal end of the housing and a proximal end of the shield comprises a barrier mechanism engageable with the other of the distal end of the housing and the proximal end of the shield wherein at least a portion of the barrier mechanism is associated with the shield and includes a break that is located external to the housing when the shield is in the extended position for cooperating with a portion of the housing to prevent transition of the shield from the extended position to the retracted position and wherein the barrier mechanism further includes an inwardly directed restraint associated with the distal end of the housing and wherein the restraint is adjacent to the break when the shield is in the extended position for preventing transition of the shield from the extended position to the retracted position.