The central question was a medical one: did he lose his life because of a heart attack or because of internal bleeding?
The central question at the inquest into the death of Ian Tomlinson, who died in the City of London during the G20 demonstrations of April 2009, was a medical one: did he lose his life because of a heart attack or because of internal bleeding?
The evidence was complicated because Tomlinson was a chronic alcoholic with a diseased liver who was more susceptible to injury than a healthy person.
Freddy Patel was the first pathologist to examine Tomlinson's body and the only expert to declare that the newspaper seller died of coronary artery disease.
Patel was opposed by all three pathologists who conducted subsequent autopsies on the 47-year-old.
Nat Cary, the second pathologist to examine Tomlinson's body, said there was "only one real possibility" over the death: that Tomlinson died because of internal bleeding in his abdomen area, most probably his liver.
Cary pointed out that footage showed the newspaper seller falling "awkwardly" after being pushed by PC Simon Harwood. His elbow became trapped between his torso and the pavement. Cary said this could have caused the "blunt force trauma" that injured his abdomen.
Cary was backed by Kenneth Shorrock and Ben Swift, two other pathologists who examined Tomlinson's body.
Graeme Alexander, a liver specialist, and Robin Williamson, a consultant surgeon, further experts called to give evidence, also said that Tomlinson was likely to have died from internal bleeding.
It was accepted that Patel, 63, was at a disadvantage when he conducted his postmortem two days after Tomlinson's death because he had not seen footage of the newspaper seller's encounter with Harwood.
Patel was asked by police to "rule out any assault or crush injuries associated with public disorder" and he was told that Tomlinson was an alcoholic who had been sleeping rough for 20 years.
The pathologist said he concluded that Tomlinson died of an arrythmic heart attack, through a "process of elimination", despite discovering that the man had suffered a "large intra-abdominal bleed".
Although Tomlinson had an injured liver and blood clot, Patel said he was unable to find an injury he believed would have accounted for the severe bleeding. He concluded that Tomlinson had died of a heart attack, stating that his most blocked artery was 85% narrowed.
That estimate was contradicted by Mary Sheppard, a coronary pathologist, who told the inquest the same artery was more likely to be about 50% narrowed.
Worse still for Patel, a consultant cardiologist, who was asked to analyse the electrocardiogram (ECG) readings taken by paramedics when they attached Tomlinson to a defibrillator, said the readings were "entirely inconsistent" with the heart attack theory.
The arrhythmic type of heart attack, Patel said Tomlinson had suffered, would have occurred with a wobbling of the heart known as ventricular fibrillation.
Kevin Channer, a heart specialist, said the ECG readings indicated that ventricular fibrillation had never happened. "In my opinion it is entirely inconsistent that his collapse was due to a primary cardiac problem," the professor said.
On the other hand, the chart readings were consistent with severe blood loss, Channer said.
Presented with this new evidence Patel changed his position, speculating that Tomlinson could have suffered a "very transient" form of arrhythmic heart attack, recovered spontaneously and then lost consciousness.
The most crucial change in his evidence related to the fluid found in Tomlinson's abdomen. After discovering that the pathologists had contradicted his findings and had concluded that the newspaper seller died of internal bleeding, Patel altered his description of the fluid; he stated that rather than blood it was mostly ascites, a bodily fluid found in patients with liver disease.
The other pathologists relied on Patel's description of the fluid because he said he had inadvertently discarded the sample.
Summing up the evidence the judge, Peter Thornton QC, sitting as assistant deputy coroner at the hearing at the International Dispute Resolution Centre, in Fleet Street, London, also reminded the jury that Patel had been suspended twice by a General Medical Council disciplinary panel in recent months over botched postmortems and for dishonesty; and one of the findings against him was that he had shown inflexibility over taking on new information.
Thornton also advised jurors to consider why Patel had repeatedly altered his position. "You must ask yourselves why this has happened," he said. "Is there a good reason for those changes, which justifies and support his original cause of death, or is his credibility as an expert witness no longer intact?"