Russian opposition leader Alexei Navalny demanded Monday that Russia return the clothes he was wearing on the day he fell into a coma in Siberia, calling it “a crucial piece of evidence” in the nerve agent poisoning he is being treated for at a German hospital. In a blog post Monday, Navalny said the Novichok nerve agent was found “in and on” his body, and said the clothes taken off him when he was hospitalized in Siberia a month ago after collapsing on a Russian flight are “very important material evidence.” Navalny, Russian President Vladimir Putin’s fiercest critic, fell ill on a domestic flight to Moscow on Aug. 20, was brought to a hospital in the Siberian city of Omsk and was transferred to Germany for treatment two days later.