Homicidal methanol poisoning in filicide–suicide

Introduction

Methanol is a clear, colourless and volatile liquid with a sweet odour. When ingested, it is rapidly absorbed from the stomach and intestines. Firstly, it converts to formaldehyde by alcohol dehydrogenase and then to formic acid by aldehyde dehydrogenase. Formic acid is responsible for the toxic effects producing severe anion gap metabolic acidosis. Typically, there is a lag period of about 12–24 h before manifestation of toxicity due to the slow conversion of methanol to formaldehyde and formic acid; however, it can occur within 6 h. ¹ Clinical manifestations include headache, confusion, nausea and blurred vision, ataxia, progressing to dyspnoea, hypotension and death. The toxic dose of methanol is 10–30 ml and lethal above 60–240 ml. The lowest reported lethal dose is 30 ml. Blood concentration over 20 mg/100 ml is toxic, over 50 mg/100 ml is associated with severe toxicity and over 90 mg/100 ml is lethal. ² The fatal period is about 6–36 h. ³

Methanol poisonings are mostly accidental due to consumption of cheap illicit liquor containing methyl alcohol. Homicidal methanol poisoning is not common. We report a rare case of a filicide–suicide in which an 18-year-old youth was killed by methanol poisoning.

Case report

An 18-year-old boy was found dead in the bedroom of his house by his grandfather who alerted the police. A handwritten note addressed to the grandfather from his son and written in English was recovered from the crime scene which stated the author was in debt and had suffered financial loss in running his chemical factory: ‘he has to go with us’. The grandfather informed the authorities that the child was mentally and physically challenged. The previous night, the parents had spent some time with their son and fed him. When he went to sleep, they went to a party but did not return till the morning. Later in the day, police recovered two dead bodies from a railway line who were subsequently identified by the grandfather as the parents of the dead boy. A passerby saw the couple jumping in front of a running train. Police also recovered their vehicle near the railway line, 5 km away from their home. On further investigation, it was discovered that methanol was given to the son by his father disguised as medicine after dinner and this put him to sleep.

Postmortem examination on the body of the boy was done on the next day. He had poliomyelitis of his right side. There was no external injury present over the body. Nails and lips were cyanosed. Food particles were present in the respiratory tract. Stomach contents had an alcoholic smell with congestion of the mucosa. Toxicological analysis revealed ethyl alcohol at a concentration of 81.8 mg/100 ml and methyl alcohol at a concentration of 39.5 mg/100 ml of blood. The cause of death was due to methanol poisoning.

Discussion

Methanol poisonings are mostly accidental due to consumption of adulterated alcoholic drinks and sometimes from household products containing methanol. As per WHO, outbreaks of mass methanol poisoning occur when methanol is added to illicitly produced alcoholic drink. ⁴ Numerous such outbreaks occurred in recent years with case fatality rates of over 30% in some instances. Fatal cases of intentional methanol poisonings have also been reported.^5,6

Homicidal poisoning by methanol is rare with only two cases reported to date. In one case, reported by Pearson et al., ⁷ a 37-year-old male died due to methanol poisoning with methanol level of 75 mg/100 ml in serum. Source of methanol was a bottle of sport drink, which he used to drink regularly and which was prepared by a family member. In another case, reported by Beno et al., ¹ a 21-month-old boy was poisoned with methanol by a caretaker. Methanol level was 230 mg/100 ml. The purpose was to frame another caretaker for his death.

This case represents a rare scenario of fatal homicidal methanol poisoning, a filicide–suicide. The parents were depressed due to financial loss. The motive was probably altruistic intended as their son was mentally and physically challenged and could not survive on his own. In a study by Hatters Friedman et al., ⁸ parental motives for filicide–suicide included altruistic and acutely psychotic motives. The study also indicated that the parents frequently showed evidence of depression or psychosis and had had prior mental healthcare.

In our case, the exact source of methanol could not be found. However, it was revealed on an investigation that his father was running a chemical factory where methanol was being used.