In his report, the United Nations's Special Rappotreur Philip Alston wrote: "Since the video's release, the government of Sri Lanka has claimed that the video is a fake.
"Over the past four months, I have been engaged in a series of communications with the government about this video, in which I requested it to conduct an independent investigation.
"While the Government initially refused to do so, on 7 September 2009, it issued a response stating that it had commissioned four separate investigations, and that they 'have now scientifically established beyond any doubt that this video is a fake'.
"At the time, I expressed concern about the objectivity of the investigations, in part because two of the 'independent experts' worked for the Sri Lankan armed forces.
"Some of the reports seemed more impressionistic than scientific, and I have never been provided the full version of the reports.
"I decided that it was incumbent upon me to commission independent and impartial evaluations of the videotape.
"I retained three experts: in forensic pathology (Dr Spitz), forensic video analysis (Mr Spivack), and firearm evidence (Mr Diaczuk).
"Together, the reports by these experts strongly suggest that the video is authentic.
"A Sri Lankan expert stated that there was no recoil or movement of the weapon discharged.
"However, Mr Spivack and Mr Diaczuk described the recoil visible on the video, and the way in which the movement was consistent with firing live ammunition.
"A Sri Lankan expert stated that the lack of audio synchronization with the video indicated manipulation. However, Mr Spivack stated that the video/audio synchronization in the video was well within acceptable limits, and that audio can be ahead or behind video, subject to various variables.
"A Sri Lankan expert stated that the movement of the second victim after being shot was not consistent with the normal expected reaction. However, Mr Spitz stated that the movement was entirely consistent with the manner in which the individual was apparently shot.
"A Sri Lankan expert stated that while wind could be heard on the audio, it was not evident in the video.
"Mr Spivack however described multiple places in the video where there is clear evidence of wind.
"Sri Lanka’s experts argued that the footage was likely recorded on a digital camcorder, and not a mobile phone.
"Mr Spivack concluded that the metadata he retrieved from the video was entirely consistent with multimedia files produced by mobile phones with video recording capability, and that it would have been very difficult to alter the metadata."