"There is credible evidence, warranting further investigation of high-level Saudi officials' individual liability, including the Crown Prince's", she said.
A known critic of the Crown Prince - especially in his columns for the Washington Post - many suspected the Saudi hierarchy were involved in his demise. Unlike many other news organizations, we have not put up a paywall. The murder sparked global outrage, including in Hollywood, where companies had eagerly courted the prince and Saudi money as the oil-rich kingdom began opening up its entertainment market.
"It entailed training, with two Saudi attaches from Istanbul flying to Riyadh for "top secret", "urgent" training and preparation, and it required planning and execution in Istanbul", the UN's special rapporteur for extrajudicial killings wrote in a report for the Human Rights Council. "The Crown Prince willingly took the risk that other crimes, such as the killing of Mr. Khashoggi, would be committed, whether or not he directly ordered the specific crime", she said.
Saudi Arabia initially offered multiple shifting accounts about his disappearance, but as pressure mounted the kingdom eventually settled on the explanation that he was killed by rogue officials in a brawl inside their Istanbul consulate.
Khashoggi's killing provoked widespread disgust and damaged the image of the crown prince, previously admired in the West for pushing deep changes including tax reform, infrastructure projects and allowing women to drive.
Sen. Lindsey Graham, R-S.C., a close ally of the president, said in a statement at the time, "While I understand that Saudi Arabia is a strategic ally, the behavior of Mohammed bin Salman can not be ignored".
His body was dismembered and removed from the building, the Saudi prosecutor has said, and his remains have not been found.
Saudi Minister of State for Foreign Affairs Adel al-Jubeir said on Wednesday that the United Nations report regarding Jamal Khashoggi's murder "has clear contradictions and baseless accusations, which hurt its credibility".
Asked if universal jurisdiction meant potential arrests of suspects overseas, Callamard said: "If and when the responsibility of those individuals has been proven, including the responsibilities of a level that warrant arrest, absolutely".
The trial of the 11 suspects now taking place in Saudi Arabia should be suspended, according to Ms Callamard, because this was an worldwide crime, over which there is universal jurisdiction. The report concluded that any campaign against dissidents and political opponents would not be possible without the crown prince's "agreement of acquiescence".
In a conversation with Khashoggi, an official told him he would have to be taken back to Saudi Arabia. However, Callamard was not able to visit Saudi Arabia and said officials never responded to her petitions to visit the country. "Now is not the time to do business as usual with Saudi Arabia". President Donald Trump has defended U.S. -Saudi ties in the face of global outcry over the slaying.
Saudi Arabia has said it wants to build nuclear power plants in the Middle East with help from US companies, but it has so far refused to sign an agreement which would ensure that it does not develop nuclear weapons and include a restriction on uranium enrichment and reprocessing spent nuclear fuel.
Separately, the Government Accountability Office (GAO) is reviewing the executive branch's negotiations with Saudi Arabia on nuclear energy since 2009.
Saudi Arabia is the United States' largest arms client, with over $129 billion in approved purchases.