A rabbit punch is a blow to the back of the head or to the base of the skull. It is considered especially dangerous because it can damage the cervical vertebrae and subsequently the spinal cord, which may lead to serious and irreparable spinal cord injury. A rabbit punch can also detach the victim's brain from the brain stem, which can kill instantly.
The rabbit punch is illegal in boxing, MMA, and other combat sports that involve striking. The only exceptions are no-holds-barred events such as the International Vale Tudo Championship (prior to rule changes in mid-2012).
On June 29, 2014, soccer referee John Bieniewicz was punched in the neck by Baseel Abdul Amir Saad, an upset player in an amateur match he was officiating in Livonia, Michigan, a suburb of Detroit. Bieniewicz died two days later of his injuries, and Saad was charged with second-degree murder. Bieniewicz’s autopsy showed that the force of the impact on the left side of his neck just below the base of his skull had resulted in a rare injury with twisted and torn arteries around the base of his skull, knocking him out before he hit the ground. 
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