It was in the final stages of the prosecution evidence that Robin Keeley, the scientist who found the firearms residue particle, entered the witness box. A small, serious man with mousey hair and large spectacles, he proved to be the sort of expert witness who constantly qualifies both his own remarks and those of his questioners. Led by Pownall, he explained what primer discharge residues were and how the particle found on the coat, comprising lead, barium and aluminium, was a chemical match for the particles produced when Dando was shot. Asked how strong the link was in scientific terms, he seemed less than enthusiastic. Such particles were never unique to a particular gunshot, he said, in fact the five basic kinds of primer discharge were 'all as common as each other'. He went on: 'The most you could say is that it could have come from that ammunition - or any other ammunition which had the same composition.' This was not what the prosecution wanted to hear, so Pownall tried again: how common were particles containing the three elements lead, barium and aluminium? 'Not uncommon,' came the firm answer. 'Ammunition with aluminium primers is not un-common.' There followed an hour or more of questioning in which nothing much went right for the Crown, and it reached its climax with a strange revelation. Keeley had had a Remington 9mm round taken from the laboratory storeroom and fired, and when he compared the residue from that with the residues found at the Dando murder scene they did not match. Whether this was important - and Keeley insisted that it was not - scarcely mattered; it was utterly baffling. Mansfield by now was laughing openly and it was fortunate for the prosecution that this chaotic exchange took place late on a Friday afternoon, so that when Pownall and Keeley resumed the examination after the weekend break some of the damage could be repaired. Reluctant though he was to endorse the particle as a firm link between George and the murder, the scientist was even more reluctant to accept that it had arrived on the coat, as the defence suggested, by innocent contamination. It was most unlikely, he thought, that it had got on to the coat either during the search or at the Amelia Street studio. His views were endorsed by a second prosecution expert in this field, Graham Renshaw, who suggested at one stage that the chances of such contamination were akin to those of winning the lottery. Although on reflection he shortened those odds somewhat, he remained of the view that the probability was low.
