One hypothesis for Narcisse's account was that he had been administered a combination of psychoactive substances (often the paralyzing pufferfish venom tetrodotoxin and the strong deliriant Datura), which rendered him helpless and seemingly dead.
[2][1][3] He recounted that he had been conscious but paralyzed during his supposed death and burial, and had subsequently been removed from his grave and forced to work at a sugar plantation.
[1] Per his account, after his apparent death and subsequent burial on May 2, 1962, his coffin was exhumed and he was given a paste (possibly made from Datura, which at certain doses has a hallucinogenic effect and can cause memory loss).
Subsequent research has discredited Davis's tetrodotoxin-zombie hypothesis by using analytical chemistry-based tests of multiple preparations, and review of earlier reports (see below).
[9][10][11] While in these popular accounts, and in Haiti, tetrodotoxin is thought to have been used in Vodou preparations, in so-called zombie poisons, subsequent careful analysis has repeatedly called these accounts and early analytical studies into question on technical grounds; moreover, they have failed to identify the toxin in any such preparation,[9][10][11] such that discussion of the matter of tetrodotoxin use in this way has all but disappeared from the primary literature since the early 1990s.
Kao and Yasumoto concluded in the first of their papers in 1986 (and remained unswerving on the matter in their later work) that "the widely circulated claim in the lay press to the effect that tetrodotoxin is ... causal agent" in a "zombification process" is, in their view, "without factual foundation".
[7] Davis responded formally to the charges, arguing the variability of the preparations (as cause for Kao's inability to find the toxin in any) and possible ineptitude in dissolving the toxin by the otherwise admittedly expert Kao, and speculating on the presence of "other ingredients" in the preparations to "enable transport across the blood–brain barrier" thus providing the needed "reduction of three orders of magnitude" of the amount needed to result in the claimed effects, and arguing that "only when the bokor ... causes others to believe the victim is dead and then revived" do his efforts become apparent, and that only a single "success ... would be sufficient to support the cultural belief in the ...