Emmerson's former clients include WikiLeaks founder Julian Assange (in connection with an attempt to extradite him to Sweden); GCHQ whistleblower Katharine Gun (who was prosecuted under the UK's Official Secrets Acts following the 2003 invasion of Iraq); and Marina Litvinenko (the wife of former Russian FSB officer Alexander Litvinenko, who was assassinated in London in 2006 using the radioactive isotope Polonium 210). Emmerson also represented Abdelbasset al-Megrahi (the Libyan intelligence officer convicted of the Lockerbie bombing) in his appeal against conviction in Scotland, and subsequently acted for Abdullah Al-Senussi, the former head of national security to Colonel Gaddafi, in proceedings before the International Criminal Court.