The results of the extended analyses, especially the stomach contents examination, indicated the oral route of methadone administration during formula feeding. Based on data presented in the relevant literature, the demonstrated methadone levels in the stomach contents and blood were sufficiently high to rule out the possibility of ingestion of the xenobiotic with mother’s milk. This conclusion was also supported by the negative findings of DNA tests in the stomach contents. The time of the methadone administration could not be determined from the toxicological results of investigations of the biological materials. Given the findings of low concentration values of methadone and its metabolite in the liver and kidney, as well as the simultaneous presence of the medication in the stomach and urine at concentrations exceeding the level observed in the blood, the examiners ruled out chronic methadone ingestion in favor of methadone administration shortly before death. The primary cause of death was accepted as methadone poisoning, which led to vomiting, aspiration of stomach contents, and choking. The issue of method of methadone administration was not explained. 3 tables and 8 references