Further observations on plastic bag asphyxia using helium gas

Helium Suicide, a Rapid and Painless Asphyxia: Toxicological Findings

Suicide by helium inhalation has become increasingly common in the last few decades in Europe and the US because it produces a quick and painless death. Inhaled-gas suicides can easily be assessed through death scene investigation and autopsy. However, helium is a colorless and odorless inert gas that unfortunately cannot be detected using standard toxicological analysis. A successful gas analysis was performed following the suicide of a 17-year-old female. For the detection of helium, central/peripheral blood samples and gaseous samples from the esophagus, stomach, and upper and lower respiratory airways (from the trachea and the primary left and right bronchia) were collected with a gastight syringe, ensuring minimal dilution. Qualitative analyses were positive in all gaseous samples. Quantitative analyses were performed using a special gas-inlet system with a vacuum by which the sample can be transferred to a mass spectrometer, reducing the risk of contamination. Helium concentrations were 20.16% from the trachea, 12.33% from the right lung, and 1.5% from the stomach. Based on the high levels of helium, the cause and manner of death were assessed as asphyxia suicide by inhalation of helium. Therefore, toxicological analyses should always be applied in order to gain evidence of inhaled gas in gaseous samples.

How common are suicides using nitrous oxide?

Analysis of autopsy cases of suicide from Forensic Science South Australia files (2003–2017) where helium, nitrogen or nitrous oxide gas had been used revealed that only 2/58 (3.5%) cases utilised nitrous oxide; the remainder of cases had used helium or nitrogen. The two cases are presented here. In case 1, a 48-year-old man was found completely encased in a plastic bag with a hose connected to an opened cylinder of nitrous oxide. In case 2, a 27-year-old woman was found with a plastic bag over her head, tied around her neck, with a tube connected to a small canister of nitrous oxide. There were approximately 20 empty canisters of nitrous oxide nearby. Death in both cases was due to nitrous oxide augmentation of plastic bag asphyxia, manner suicide. The relative ease with which helium and nitrogen cylinders containing large amounts of gas can be obtained may explain the low numbers of suicides utilising nitrous oxide.

Nitrogen inhalation suicide pacts

Suicide pacts usually result in simultaneous deaths by mutual arrangement. While nitrogen and helium gas inhalation are being increasingly used in solitary suicide attempts, for some reason they have been rarely utilised in suicide pacts. A search of autopsy files at Forensic Science SA over a 15-year period (2003-2017) was undertaken to determine how often this method of joint suicide occurs. Only two cases were found. Case 1 comprised a 64-year-old husband and wife (who had a history of multiple sclerosis). They were found deceased in a vehicle with two empty cylinders of nitrogen gas. Case 2 comprised an 87-year-old man (who had a history of ischaemic heart disease) and his 81-year-old wife who were found deceased with plastic bags over their heads, with plastic tubes connecting the bags to opened cylinders of nitrogen. The deaths in all cases were due to nitrogen-induced asphyxiation, in the latter instance augmenting plastic-bag asphyxia. Although suicide pacts have previously usually involved carbon-monoxide toxicity or drug overdose, it is possible that dissemination of information on the use of inert gases in individual suicide attempts may alter the methods used in future.