The chief resident-in-training at our hospital was putting a patient on a bypass machine in preparation for open-heart surgery.
The patient, who happened to be a policeman, had his aorta clamped, and then circulation was stopped so that the operation could be done on a non-beating heart.
The atmosphere in the operating room had been serious until the clamp was applied. Just then the attending physician remarked,
"Hey, you just arrested a cop!