People protest the alleged murder of journalist Jamal Khashoggi, at the Saudi Arabian Embassy in Washington on Oct. 10. (Jacquelyn Martin/AP)

LET’S BE clear: The Saudi “investigation” of the disappearance of journalist Jamal Khashoggi, which the Trump administration contends needs to be given more time to reach conclusions, does not exist. The Saudi leadership under King Salman and Crown Prince Mohammed bin Salman, like the Turkish government, knows very well what happened inside the Saudi Consulate in Istanbul on the afternoon of Oct. 2. Though they pretend otherwise, so do President Trump and his top aides, who have access to U.S. intelligence reports that are being withheld from Congress.

The basics have been widely reported. The Turks have told U.S. officials and journalists that they possess audio and video recordings documenting the brutal murder and dismemberment of Mr. Khashoggi, whose fingers and head were reportedly cut off by a Saudi autopsy specialist who coolly listened to music on headphones as he butchered. The Turks have released photos and passport and flight records of the 15-member team that allegedly carried out the operation.

The documents show that at least four men closely associated with Mohammed bin Salman, including three members of his personal security team, flew to Istanbul the day of the killing, according to the New York Times. One man who has traveled extensively with the crown prince was photographed entering the consulate before Mr. Khashoggi’s arrival. The Post has reported that U.S. intelligence intercepts detected Mohammed bin Salman discussing plans to lure Mr. Khashoggi back to the kingdom so he could be detained. Experts on Saudi Arabia say it is unthinkable that the Istanbul operation would have been carried out without the crown prince’s knowledge and approval.

So, as we said, there is no investigation; the crown prince cannot investigate himself. Rather, Mr. Trump and Secretary of State Mike Pompeo are conspiring with the Saudi leadership, buying time for them to construct a cover story that will deflect a wave of international outrage and discourage Congress from sanctioning the regime. Mr. Trump said Thursday that he believed Mr. Khashoggi was dead and that there would be “very severe” consequences — just as reports surfaced that Riyadh was preparing to pin blame on a senior intelligence official, while excusing the king and his son.

That dodge would allow Mr. Trump to perpetuate what has been an ill-advised policy of close collaboration with the crown prince, despite what is now a long history of reckless actions that have undermined U.S. interests, including the administration’s campaign against Iran. Mr. Trump keeps harping on the $110 billion in weapons sales he claims the Saudis have committed to; but there have been no actual deals on his watch.

The attempted coverup may not work, given the amount of public evidence already implicating Mohammed bin Salman. But the full truth of what happened to Mr. Khashoggi may never emerge without an independent international investigation. A coalition of human rights organizations has joined the calls for such a probe, which could be launched by the U.N. Security Council or the secretary-general.

Similarly, accountability for Mohammed bin Salman and his associates will likely require action independent of Saudi Arabia and the Trump administration. Congress should conduct its own investigation and prepare comprehensive sanctions, as it did in the case of Russia. U.S. businesses, which have already boycotted an investment conference headed by the crown prince, should continue to shun him. The attempt by the Saudi leader and his U.S. accomplices to cover up and excuse an act of pure evil cannot be allowed to succeed.