When the Biden administration filed a legal brief last week calling for the Saudi crown prince, Mohammed bin Salman, to be granted sovereign immunity in a civil case involving the murder of the journalist Jamal Khashoggi, it said it was strictly a legal determination that did not reflect its views on the “heinous” killing.

“In every case, we simply follow the law. And that’s what we did,” Antony Blinken, the US secretary of state, later said.

But a close examination of the Biden administration’s actions, including interviews with legal experts and people who closely followed the matter, suggest the controversial decision was anything but straightforward.

Beginning last summer, the administration’s decision to delay action and seek months of legal extensions before submitting its views on the matter before a US judge offered Saudi Arabia an unprecedented opportunity to protect Prince Mohammed through a legal manoeuvre that put him above the law and out of the reach of the US legal system. Once this had happened, the Biden administration in effect said its hands were tied.

“If you look at the sequence of events, it is hard not to see this was a battle between Biden and Mohammed bin Salman playing out,” said one close observer, who asked not to be named so they could speak candidly. “I would hate to imagine that there was bartering over our judicial system and that integrity was up for grabs.”

The US government was first invited to get involved in the civil case against Prince Mohammed on 1 July by the US district court judge John Bates. At the centre of the request was a lawsuit filed in 2020 against the crown prince and his associates by Hatice Cengiz, Khashoggi’s fiancee, which accused Prince Mohammed and his associates of conspiring with premeditation to kidnap, torture and murder Khashoggi in the Saudi consulate in Istanbul in 2018.

Bates’s request was straightforward. He gave the administration 30 days – until 1 August – to submit a “statement of interest” and weigh in on whether the heir to the Saudi throne ought to be granted sovereign immunity in the case, or tell the court that it did not wish to make a statement. He also wanted the administration to weigh in on how the court might reconcile protections that are given to foreign leaders and those who are using a US law that allows victims of torture or extrajudicial killings to hold perpetrators accountable.

At that time, Prince Mohammed was – clearly – not a sovereign. In Saudi Arabia, that distinction belonged at the time solely to his father, King Salman.

Harold Koh, a former legal adviser to the state department during the Obama administration who is now a professor of international law at Yale Law School, said the US had competing interests at the time. On the one hand, the US asserts reciprocal principles of immunity so that its own head of state will be offered protection from legal courts. But that had to be weighed against Biden’s statements about human rights being at the centre of his administration’s foreign policy and “autocrats understanding that the president means what he says”.

“All things considered, silence would have been the better way to balance those competing national interests,” Koh said, adding that there would have been “ample precedent” for the state department to stay silent.

On 15 July, Joe Biden met Prince Mohammed in Jeddah, a meeting that started with a fist bump and was meant to “reset” his relationship with a leader he once called a pariah. It would later emerge that the meeting was also the start of a campaign by the administration to try to persuade the Saudis not to cut oil production before the US midterm elections.

Back in Washington, just a few days later on 18 July, the US asked Judge Bates for an extension, saying it needed time to consult multiple entities within the administration with respect to “complex issues of international and domestic law”. The court agreed, giving the US until 3 October to respond.

Weeks later, on 23 September, Brett McGurk, a Middle East policy coordinator for the US National Security Council (NSC), and Amos Hochstein, a US senior adviser for energy security, visited Jeddah again, ostensibly to discuss energy policies.

Days later, on 27 September, the Saudi royal court announced that Prince Mohammed had been named prime minister, a role that had been and usually is held by the Saudi king. Observers noted that the apparent promotion did not confer any major new duties or powers to Mohammed bin Salman. Human rights defenders saw it as a ploy to influence the US recommendation on sovereign immunity, which was due about a week later.

The US government, citing “changed circumstances”, requested a second extension to prepare its response and was granted one, until 17 November. A few days after it missed its 3 October deadline, Opec+ announced it was cutting oil production by 2m barrels a day, in what was seen by Democrats as an attempt by the kingdom to interfere with the US election and side with Russia over US interests.

Biden promised that Saudi Arabia would face “consequences” for the decision, but has not articulated any specific actions he planned to take against the kingdom. On 17 November, just hours before a midnight deadline, the administration filed a notice that it believed Prince Mohammed, as prime minister, deserved to be treated as a sovereign as a standard matter of international law.

An NSC spokesperson told the Guardian that the US president was briefed on the immunity decision, which was based on “well-established principles of common law”.

When the Guardian asked the spokesperson if any US official ever suggested to Saudi Arabia that Prince Mohammed could be appointed prime minister before the matter was public, the spokesperson said: “This was an independent decision made by Saudi Arabia.”

People familiar with the matter say legal questions about Prince Mohammed’s status were hotly debated inside the state department, where views about the best course of action differed.

In debates within the administration, senior officials such as McGurk who have sought to promote the rehabilitation of the Saudi-US relationship have edged out policy objectives focused on human rights.

“This administration made the decision it did because Mohammed bin Salman is prime minister. But they dragged their feet so much … This was clearly a policy decision in that they waited and stalled,” said one person who has advocated for human rights to have more prominence in decisions around policy.

Leaders like Prince Mohammed were “legitimately worried” when Biden first came into office and vowed to make the Saudi heir accountable for human rights violations.

“And when they got into office, the execution was not there,” the person said. Even when Biden made the decision to release a declassified intelligence report that found Prince Mohammed had likely ordered the murder, there were no sanctions against him.

The person added: “That set the stage and indicated the rhetoric was not matched by substance.”