There's no story from the parents as to what happened. The closest the paper gives to explaining the situation directly is at the end of the Case Report: "Addi

There's no story from the parents as to what happened. The closest the paper gives to explaining the situation directly is at the end of the Case Report: "Additional history disclosed an unstable motel-living situation and parental admission of drug possession, including cannabis." In the midst of the toxicological analysis, it mentions that the THC metabolites they observe were "most likely secondary to ingestion" and it later says, given that they observed various metabolites but not the primary compound itself, "the authors deduce that cannabis consumption occurred within the recent two to six days, assuming this was a single, acute high-potency ingestion." So, most likely what happened is that the parents carelessly left some edibles around, and the infant toddled over and put one in his mouth. Infants put everything in their mouths, so an accidental exposure sounds plausible- albeit criminally negligent. I'd presume the parents have been charged accordingly.