- The touch of death is known in Cantonese as Dim Mak and in Japanese as Kyusho Jitsu. Traditional Chinese medicine claims that chi or energy flows through the body along lines called meridians. A study published online by the British Medical Journal found that Acupressure (applying pressure with the thumbs or fingertips to the same points on the body stimulated in acupuncture) seems to be more effective in reducing low back pain than physical therapy.
The related claim that placing pressure on these meridian points might bring about better balance, circulation of fluids like blood and lymph, and metabolic energies in the body has little to no scientific evidence. It is also further claimed that a blow or squeeze applied to certain other pressure points on these lines will influence the victim's chi, leading to incapacitation or death.
- Per Terry C et.al.'s research in 1999, unresponsiveness have been observed due to pressure point technique application in volunteers performing martial arts demonstration carried out at a medical center hospital. The results of that study of kyusho jitsu pressure point techniques used in martial arts showed that there was no change in BP, cardiac rate or rhythm.
Conclusions: The exact mechanism for the state of unresponsiveness produced by application of pressure point techniques is uncertain. There is no evidence of reduced cerebral blood flow or of other dangerous physiologic changes and it is not related to a significant cardiac or pulmonary process. Source: Physiologic study of pressure point techniques used in the martial arts
TL;DR: The touch of death has no basis in reality, however, there has been occasional instances of less forceful blows causing death and the exact mechanism causing this phenomenon is unknown to science at the moment.
Having browsed the medical literature, I'd say the verdict on whether this mysterious Oriental skill has any basis in reality is as follows: The touch of death, no. The less forceful blow than you might expect of death, occasionally yes. Source: Straight dope