In this Dec. 15, 2014 file photo, Saudi journalist Jamal Khashoggi speaks during a press conference in Manama, Bahrain. An independent U.N. human rights expert investigating the killing of Saudi journalist Jamal Khashoggi is recommending an investigation into the possible role of Saudi Crown Prince Mohammed bin Salman, citing "credible evidence." (AP Photo/Hasan Jamali, File)

The United Nations Special Rapporteur Agnes Callamard said Wednesday in a report on the killing of journalist Jamal Khashoggi that substantial evidence points to a state-sponsored execution likely ordered by Saudi Arabian officials.

Callamard called for a U.N. criminal investigation into Saudi Arabian Crown Prince Muhammed bin Salman and the role he likely played in ordering the 2018 execution.

Khashoggi entered the Saudi Consulate in Istanbul, Turkey on October 2 and was never seen again. Recordings provided by Turkish officials illuminate the final moments of Khashoggi’s life. He was injected with a sedative then strangled with a plastic bag before his body was dismembered and removed in bags.

Saudi Arabia initially claimed no knowledge of the killing, but later arrested 21 individuals the state claims were “rogue actors” operating without orders. American intelligence efforts and the UN report have both concluded that the killing could not have been done without the knowledge of the crown prince.

Saudi Arabia is trying 15 individuals for the murder but has not allowed foreign investigators to witness the trial, leading Callamard to believe the monarchy is concealing evidence and obstructing justice.

“The investigation and subsequent prosecution should comply with international legal standards, and that demands the highest levels of transparency and impartiality,” Callamard said in the report.

The Saudi authorities have not even disclosed publicly the identities of the accused, their roles in relation to the government, or the details of the charges they face. Court proceedings have been held behind closed doors.

Callamard has called for greater transparency into the trials and believes an international investigation into the role the crown prince played is essential to finding justice for the family Khashoggi left behind.

Khashoggi’s killing weighs heavily on US negotiators and international law. Beyond the illegality of executing political dissidents, the execution of Khashoggi violates multiple international laws intended to prevent state enforcement of policies and laws on foreign soil.

The investigation into his death may create an increase in the already-strained diplomatic negotiations aimed at preventing an increase in military action in the Middle East.

The US has acknowledged the likely role of Saudi Arabia in Khashoggi’s death but official rebuke has been timid. The US is currently involved in a war of posturing with Iran and counts Saudi Arabia as a regional foil against radical Islamic terrorists sponsored by Iran.

Should the rhetoric with Iran turn to military action, the US will need the cooperation of allied nations that include Saudi Arabia to effectively wage war in the Middle East.