Some experts have questioned whether Arafat could have died of polonium poisoning, pointing to a brief recovery during his illness which is not consistent with radioactive exposure. They also noted he did not lose all of his hair.
But Professor David Barclay said neither fact was inconsistent with the findings.
Since polonium loses 50% of its radioactivity every four months, the traces in Arafat's corpse would have faded so far as to have become untraceable if the tests had been conducted a couple of years later, Professor Barclay said.
More top news
Guillier conceded a "severe defeat" defeat to his supporters as the result came in.