The Vulcan death grip was a fictitious Vulcan technique invented by Spock. Its application was similar to that of the mind meld, except that it was administered with two hands, and without speaking. It is supposed to appear to be deadly pressure applied to the face and head.
History of use
In 2268, Spock used the so-called "Vulcan death grip" on Captain James T. Kirk as a means to fool the Romulans into believing Kirk was dead, so as to bring him back on board the USS Enterprise without causing suspicion. Spock claimed that he had used the death grip instinctively, in response to an unexpected assault from Kirk. Dr. Leonard McCoy angrily spat, "Well, at least your instincts are still good, Mr. Spock. THE CAPTAIN IS DEAD!!!"
In reality, Spock had administered an especially deep nerve pinch to Kirk to falsify the latter's death, and also to block Kirk's life signs from Romulan bio-scanners. When he recovered, Kirk complained of his neck feeling like it had been twisted off.
When informed of the incident, Nurse Christine Chapel exclaimed, "But there's no such thing as a Vulcan death grip!" Kirk replied, "Ah, but the Romulans don't know that!" (TOS: "The Enterprise Incident")
Spock uses the Vulcan death grip as a threat when attempting to learn the location of a stolen protomatter warhead in the novel Foul Deeds Will Rise, with Montgomery Scott feigning shock at the idea that Spock would go that far and later teasingly wondering what they will do if people ever learn that the Vulcan death grip does not exist.
In Leonard Nimoy's television special titled Leonard Nimoy: Star Trek Memories, Nimoy mistakenly remembers that Spock had pretended to apply the Vulcan death grip to Dr. McCoy instead of Captain Kirk.
According to writer D.C. Fontana, the Vulcan death grip was actually intended to be more than just a fictitious technique. "It harks back to the days when they were savage, and emotion ruled them," she revealed. "It's not often used; it's only used in dire circumstances, probably just to protect your life."