The issue of custody is significant; in his final moments on screen Berg is wearing an orange jumpsuit of the kind familiar from Guantanamo Bay. The official reasons for Berg's arrest were "lack of documentation" and "suspicious activities". He carried sensitive electronic equipment for which he lacked documents. In custody, he was visited three times by the FBI. Such interviews are bound to have been recorded but no transcripts have been produced.
http://www.smh.com.au/articles/2004/05/28/1085641717320.html?from=top5

A US military report last month has claimed al-Zarqawi was killed in the bombing of Falluja.

Dr John Simpson, executive director for surgical affairs at the Royal Australasian College of Surgeons, told Ritt Goldstein of the Asia Times, "I would have thought that all the people in the vicinity would have been covered in blood, in a matter of seconds ... if it [the video] was genuine".

Simpson agrees with other experts who find it highly probable that Berg had died before his decapitation.