SAUDI ARABIA now has acknowledged that it lied to the world for 17 days about what happened to journalist Jamal Khashoggi when he entered its consulate in Istanbul on Oct. 2. But the new account offered by the regime of King Salman and Crown Prince Mohammed bin Salman is utterly devoid of credibility. The latest version asks us to believe that Mr. Khashoggi died after becoming engaged in a “brawl” with officials who had been sent to meet him. His body, Saudi officials told several journalists, was handed over to a “local collaborator” for disposal. That President Trump would pronounce this fable credible only underlines his shameful intent to assist in the attempt of the regime — and, in particular, the crown prince — to escape meaningful accountability.

As Mr. Trump surely knows, the new Saudi cover story is contradicted not just by evidence collected by Turkish authorities and by journalists but also by the reporting of the U.S. intelligence community. All point to Mohammed bin Salman as the instigator of a premeditated, cold-blooded and brutal murder, followed by the dismemberment of Mr. Khashoggi’s body. As The Post’s Shane Harris reported, CIA officials have listened to an audio recording in the possession of Turkish officials they say backs up their account that Mr. Khashoggi was murdered minutes after entering the consulate by a team of 15 men. The Post has identified five of those men as probable members of the crown prince’s personal security detail.

Another man positively identified as a member of the team, Salah Muhammed al-Tubaigy, is the head of forensic science at the Saudi General Security Department and a specialist in on-site autopsies. According to the Turkish account, he cut off Mr. Khashoggi’s fingers and head, after donning headphones and advising his colleagues to do the same. If, as the Saudis now contend, the security team was sent to meet Mr. Khashoggi because “there were indications of the possibility of his returning” to Saudi Arabia, why was such a man, along with Mohammed bin Salman’s personal muscle, on the mission? In fact Mr. Khashoggi, a Post contributing columnist, had no intention of returning to the kingdom. He visited the consulate in order to obtain a paper that would allow him to marry a Turkish woman, with whom he had obtained a new home in Istanbul.

In a transparent attempt to satisfy demands for accountability while protecting the crown prince, the regime arrested the members of the team sent to Istanbul and several consular employees, and fired four senior intelligence officials, as well as a top aide to the crown prince, Saud al-Qahtani. Mr. Qahtani, who drew up a blacklist of critics of the crown prince, is evidently being scapegoated for targeting Mr. Khashoggi. Here is what he tweeted last year: “Do you think I can act by myself without taking orders/guidance? I am an employee and a trustworthy executive to the orders of the king and the crown prince.”

Mr. Trump, who called the Saudi actions “a good first step,” added that he had more questions, and a White House statement promised to “closely follow the international investigations into this tragic incident.” But there are no international investigations — only the blatant coverup exercise of the Saudis and a Turkish probe that could quickly be shut down if President Recep Tayyip Erdogan finds doing so politically convenient. The only way to determine the truth of what happened to Mr. Khashoggi is a genuine international investigation, led by a U.N.-appointed panel. Secretary-General Antonio Guterres should take the initiative. Congress should launch its own investigation, including of whether the Trump administration is conspiring with Saudi officials to cover up the murder of a distinguished journalist.

In the meantime, Saudi Arabia and its regime should be treated as outlaws by all who value human rights and free expression. Businesses that withdrew this week from an investment conference in Riyadh should continue to shun contact with the crown prince; Washington lobbyists should refuse to accept more of his cash. Congress should block all arms sales and deliveries. U.S. relations and cooperation with Saudi Arabia must continue but only after they have been put on a new footing. The first step in that process is determining the full truth about the Khashoggi murder and holding its likely author — Mohammed bin Salman — fully accountable.