Analysis of blood vessels confirmed a tribute to senior al-Qaeda leader in which he broke the Wall Street Journal Daniel Pearl, according to a new report released Thursday.
Khalid Sheikh Mohammed is suspected of planning terrorist attacks of September 11, 2001, the United States.
Muhammad did not deny his involvement in the murder of Pearl, who was abducted in January 2002.
verity journalist The video has been shared over a network in nearly a month after being kidnapped, but the face of the killer who cut his throat was not visible.
U.S. officials have accused Mohammed died in 2002.
"I decapitated with my blessed right hand the head of the American Jew Daniel Pearl in Karachi, Pakistan, Mohammed said, according to a transcript the Pentagon released nearly four years. "For those who want to confirm, there are pictures of me on the Internet holding his head."
The new report removes all doubt that Mohammed personally carried out the beheading.
FBI agents and CIA used a technique called seam matching to compare the hand-killer with an image of the hand of Mohammed, the report said.
Mohamed told the FBI that senior al-Qaeda has advised him to take control of Pearl to his captors of origin, the report said.
Pearl was captured on the road to what he thought was an interview with a radical pastor. At least 27 men have played a role in the kidnapping and death - 14 of them believed to be free, says the report.
At least three militants were involved in crime, including the kidnappers led by British-Pakistani Omar Sheikh and a team of assassins headed by Mohammed, the report said.
It also highlights the obstacles the authorities in charge of the investigation, including conflicting evidence.
The Pakistani authorities released security guard, who was a key informant, and failed to follow potential leads, according to a report.
Three year project was developed by Pearl teachers and students of Georgetown University in Washington DC He was released Thursday by the Center for Public Integrity.