One of the most common misconceptions about defensive knife tactics has to do with blood loss and its relationship to stopping an attacker. While it is very true that inflicting severe bleeding wounds can ultimately take an attacker out of the fight, the time it takes for someone to bleed to unconsciousness is much longer than most people think. And every second that an armed attacker is upright and mobile, your chances of surviving the incident diminish.
Much of the misinformation concerning blood loss in knife fighting began with the work of British close-combat legend W.E. Fairbairn. His “Timetable of Death” was originally published in the 1942 book All-In Fighting and later in the 1944 classic Get Tough. This timetable consisted of a diagram of the human body identifying all the major arteries and a companion table that provided the depths below the skin of the various arterial targets and the heart. It also listed in specific detail exactly how long it would take for a person to bleed to unconsciousness and bleed to death when each of these targets was severed or punctured.
Fairbairn never revealed how he arrived at the detailed times cited in his table. So the accuracy of his data has long been the subject of speculation. Nevertheless, for decades after WWII, Fairbairn’s table was a standard reference for knife tacticians and was widely quoted by many instructors. It was even used as a reference in a major law enforcement defensive tactics/knife defense program.
Fairbairn Myth Busting
Several years ago, Christopher Grosz, a law enforcement officer and defensive tactics instructor in Littleton, Colorado, questioned the accuracy of Fairbairn’s timetable and decided to try to validate it with modern medical data. In addition to extensive independent research into the medical effects of various types of edged-weapon wounds, Grosz worked very closely with Colorado’s Arapahoe County Medical Examiner, Dr. Michael Doberson. He also enlisted the aid of acknowledged edged-weapons instructors, including yours truly.
In simple terms, the extremely fast onset of unconsciousness claimed in Fairbairn’s table didn’t correlate to many actual incidents in which victims of accidents and soldiers on the battlefield suffered serious bleeding wounds or even severed limbs, yet still managed to survive. Also, basic logic would dictate that a faster heart rate would cause more rapid blood loss and consequently quicker onset of unconsciousness and death. The fact that Fairbairn’s table totally ignored the effects of heart rate cast considerable doubt on its accuracy.
With Doberson’s guidance, Grosz developed a simple, scientifically sound method to calculate time to unconsciousness and death based on blood loss. First, he determined that blood volume and body size are a linear relationship and that the effects of blood loss are based on the percentage of overall blood volume lost. At 20% blood loss, shock ensues. Unconsciousness occurs with a 30% blood loss and death occurs when 40% of your total blood volume is lost.
Based on modern medical knowledge, Grosz then determined the percentage of total blood volume that flows through the major arteries of the body, as well as the “stroke volume”—the amount of blood pumped out by the heart with every beat. By multiplying the stroke volume times the heart rate (in beats per minute), you can determine how much blood is pumped into the vascular system in one minute. Then, by determining the percentage of that volume that passes through a particular artery and comparing that to the total blood volume, we can determine the percentage of blood loss that would occur if that vessel were severed.
