The circumstances surrounding Osama bin Laden's reported death raise urgent questions over how the US is so sure it got its man.
US officials have said DNA testing has proved the al Qaeda leader was killed in a villa in Pakistan.
They have also identified him by facial recognition.
But photographs of Bin Laden after his reported death have not been released.
The fact his body was buried at sea has so far only added to the speculation, although as a Muslim, he had to be laid to rest as quickly as possible.
Under Islamic law, people can only be buried at sea if they died there, or if there is a risk their body will be exhumed or dug up if buried in the ground.
The release of a photograph purporting to show bin Laden's corpse - which was later confirmed to be a fake - added to the confusion.
Journalists have not yet had the opportunity to ask more than a few questions of the Obama administration about details of Bin Laden's death.
A former British ambassador to the US, Sir Christopher Meyer, told Sky News: "I imagine we will see proof.
"I can't concede the US president would go out to make a statement to the world that bin Laden is dead without being able to produce evidence that he is dead.
"I think we will see some evidence - DNA or photographic - to prove there is not still some phantom Osama bin Laden riding the Tora Bora mountains."
The announcement is not the first time the world has heard of Bin Laden's death. Claims that the US and Britain kept up a pretence he was alive in order to continue their war on terror have been dismissed as conspiracy theories.
Additionally, his appearance in the December 2001 video was markedly different. He sported a black beard, not his usual grey one, his pale skin had become darker and he had a different shaped nose.
He also looked in good health - a contrast to his earlier gaunt appearance - and critics have pointed to the fact he is seen writing a note with his right hand, although he was left-handed.
In total, Bin Laden is thought to have released around 40 statements since 9/11, many of them with clear references to events at that time.
When Uday and Qusay Hussein - the sons of Iraqi dictator Saddam Hussein - were killed in a firefight with US troops, authorities relied on photographs of their bodies to convince people they were dead.
And when Saddam himself was executed, video footage of his death and subsequent photographs seemed to give final proof of his death.