The current consensus on “restraint asphyxiation” is reflected in a guidance statement of the United States Department of Justice.⁵ Any person who is restrained prone has trouble breathing when pressure is applied to his or her back or when handcuffed and “hog tied,”^2,3 and obesity exacerbates this. People’s natural reaction is to struggle more violently, which may be met with still more restraining force, resulting in greater oxygen deficiency and, in some cases, death. Risk factors include any condition, such as ischaemic heart disease or excited delirium,² that increases susceptibility to cardiac arrhythmias, as well as intoxication with alcohol or drugs.

Neurochemical abnormalities have been identified. There are fewer D₂ receptors in the centres of the hypothalamus that oppose D₁ mediated temperature increases.^1-4 This explains why those who die are invariably hyperthermic. In the series from Miami, mean body temperature was 40.6°C at the time of the first medical examination.^1-2 Changes induced by cocaine in the number and distribution of κ₂ opiate receptors within the amygdala may explain the distinctive psychotic symptoms and violent agitation.^1-5 These changes can be shown at any neurochemistry reference laboratory, provided the brain is removed and slices frozen within 12 hours. The mere presence of these changes does not prove that police misconduct or medical mismanagement did not occur, but it does prove that the patient had a disease that is usually fatal.

Death is often attributed to capsicum (pepper spray) poisoning rather than to the underlying psychiatric state. In trying to spray agitated psychotic people, police officers often miss their face and spray their back or shoulder and sometimes the faces of other officers. We use saline swabs to recover capsicum from skin and clothing of people who are alive and methanol to recover it from those who have died. There are no assays for capsicum in biological matrices, but toxicity is effectively ruled out if capsicum cannot be recovered from the facial area.

Prudent management also includes a meticulous, well photographed, neck dissection to rule out neck compression, and measurement of drug concentrations in the brain. These seem to provide an accurate picture of the pattern of cocaine use, and the use at the time of death, whereas blood measurements are often unreliable.