This explanation, based on court transcripts and interviews with the barrister who defended the University, and the clinicians and scientists who were involved with the outbreak, contradicts the conclusions of the official government enquiry, The Shooter Report.

[2][3] In the autumn of 1978, Parker, a photographer employed by the University of Birmingham and based at its medical school, contracted smallpox and died from the infection.

Shooter's conclusion was contested in the legal case – Robert Kenyon Cook versus the University of Birmingham – by an expert witness, Professor Kevin McCarthy, who considered the "duct" hypothesis impossible given the small amounts of virus that were present in the laboratory.

The magistrates found the university not guilty of charges made by the Health and Safety Executive, which left the question of how Parker had contracted the infection unanswered, although there was no doubt that the same strain of smallpox virus had been used in experiments in the laboratory.

[1] Philip Mortimer, reviewing in the journal Epidemiology and Infection, describes Pallen's "interesting tale" as a "warning to scientists" that is accessible to the general reader and relevant to professionals.