Confirming a “kill” in a targeted attack by plane or drone in hostile territory is done in the first instance by monitoring communications – mobile phones, radio etc – in the area of operations. The optimal and foolproof method of confirmation is to take a DNA sample of the victim’s remains and check it against material obtained from relatives. But that depends on access on the ground, which is unlikely in Raqqa, capital of the Islamic State.If Mohammed Emwazi, the Islamic State extremist known as “Jihadi John”, has really been killed in a US drone strike, Isis will likely eventually make its own announcement. It may also deny the US claim. Given the group’s slick propaganda abilities, any statements will be subject to close scrutiny and verification.‘Jihadi John’: high degree of certainty US airstrike killed Mohammed Emwazi, sources say Read moreInformation about the reported killing and Emwazi’s high profile suggest he was under extremely tight surveillance that is likely to have combined sophisticated technical means and human intelligence. That suggests whatever can be heard or seen remotely by US or allied intelligence can be supplemented by visual or other observations from an agent in the area.In 2011, when US special forces killed the al-Qaida leader, Osama bin Laden, in his Pakistani hideout, his corpse was transported to a ship for DNA tests that confirmed his identity before he was buried in the Arabian Sea. In Yemen, another theatre of operations against jihadi militants, Saudi Arabia regularly takes DNA samples of wanted men it has targeted. In several drone strikes against leaders of al-Qaida in the Arabian Peninsula, tests did not confirm that they were the correct target.Earlier this year, the FBI confirmed the death of a wanted Jemaah Islamiyah terorrist, Zulkifli bin Hir, after conducting DNA tests on a severed finger found at the scene of the commando raid that killed him in the Philippines. Three years earlier he had been reported killed in an airstrike.US and UK officials have both indicated there is a high degree of certainty Emwazi was killed overnight on Thursday, but have yet to present their evidence. It is likely the full details of how that evidence is gathered will not be made public.