President Rodrigo Duterte reviews police academy graduates as he arrives for the commencement at the Philippine National Police Academy in March in Cavite, Philippines. (Romeo Ranoco/Reuters)

Rodrigo Duterte is not afraid of the International Criminal Court — or so he likes to say.

Asked about the possibility of an ICC investigation, the Philippine president dismissed it with a curse. When a critic vowed to submit evidence of possible crimes against humanity, he told him to go ahead.

A year after Duterte swept to power on a promise to kill all the country’s suspected drug users, with an estimated 9,000 people dead and many missing, a growing number of experts say the Philippine president will be investigated by the ICC.

In October, when the death toll stood at several thousand, lead prosecutor Fatou Bensouda warned the country without naming Duterte directly, saying she was “deeply concerned about these alleged killings and the fact that public statements of high officials of the Republic of the Philippines seem to condone such killings.”

In the months since, Duterte’s calls to kill — or, more recently, rape — without fear of consequence have not let up, nor has the violence. Those who speak out against the killing risk public shaming, even prosecution. Domestic efforts to systematically investigate and prosecute drug war cases have thus far failed.

The office of the ICC prosecutor declined to comment on if or when it plans to pursue a preliminary examination, the first step in the process. But experts in international justice predict the court can and will move ahead — and many in Manila hope they are right.

“I think that the situation is ripe for the prosecutor to start an investigation,” said Alex Whiting, a professor at Harvard Law School who previously worked in the Office of the Prosecutor. “I’m surprised it hasn’t happened sooner.”

In a letter written from her jail cell, Sen. Leila de Lima, a longtime critic of Duterte’s human rights record who faces dubious drug charges, told The Washington Post the ICC is “the last hope for the Philippines to see an end of the killings.”

If the ICC is the last hope, it is probably a distant one, at least in terms of timing. While Philippine police and plainclothes assassins conduct daily raids in some of the Philippines’ poorest communities, often shooting to kill, the ICC operates over a span of years.

The Philippines signed the Rome Statute, the treaty that created the ICC, in 2011, which means the court has jurisdiction for crimes within its mandate committed there. However, it can only assert that jurisdiction if it is clear local authorities have failed to investigate and prosecute crimes.

In April, a Philippine lawyer, Jude Josue Sabio, hand-delivered a complaint to the ICC, accusing the president and 11 associates of mass murder and crimes against humanity. The move made headlines but will probably not sway the court either way, several lawyers said.

So far, Duterte’s strong political support, combined with his reputation for silencing critics, have kept Philippine institutions from pursuing criminal charges or from conducting any sort of comprehensive, independent investigation into the deaths.

“At the moment, we see little effort by the Philippine authorities to investigate,” said Peter Bouckaert, emergencies director at Human Rights Watch and the author of a report on extrajudicial killing in the Philippines under Duterte. “If the killings continue, and the Philippine authorities continue to block any effective domestic investigations and prosecutions, the likelihood of an ICC investigation will increase.”

There are political considerations, too. On one hand, the ICC, which started operation in 2002, has a relatively small budget and is already pursuing 10 preliminary investigations and 10 “situations under investigation.”

On the other, the court is fighting to stay relevant.

The United States and China never signed the treaty. Russia signed but never ratified and then withdrew last year, much to Duterte’s pleasure. South Africa, Gambia and Burundi have, at various times, threatened to withdraw.

The fact that the court has faced criticism, particularly criticism for pursuing too many cases in Africa, could push prosecutors to take on Duterte, experts said. In some ways, Duterte’s very public, high-profile exhortations to violence have left the court “with little choice,” Bouckaert said.

There is also the question of what a preliminary examination, even an eventual prosecution, would mean for the Philippines or for its relationship with other countries, including the United States.

In Manila, the prospect of an ICC preliminary examination is now seen as one of the last remaining ways to get Duterte’s attention — to persuade him to change course.

Though he has repeatedly dismissed the court, there is a sense in the capital that he does, in fact, fear it — or at least fears the political and economic hassles it could bring. “It may be the only thing he’s afraid of,” said a senior Western diplomat in Manila.

Although the effort to charge or extradite Duterte would take years, if it happens at all, it could have an immediate impact on his reputation at home and abroad.

Sen. Antonio Trillanes, a vocal Duterte critic, said the president could shrug off an ICC move in the short run, decrying foreign intervention and playing to national pride. But over the long run, he may have trouble defending any move that hurts the country’s standing.

“Opening a preliminary examination would send an important signal that the court’s investigators and prosecutors are watching,” said Mark Kersten, an expert on international justice at the Munk School of Global Affairs at the University of Toronto.

“While there are good reasons to be skeptical of the deterrence effects of the ICC, the fact that it even just might influence Duterte’s behavior should be reason enough for chief prosecutor Fatou Bensouda to proceed.”

The tag­line “accused of crimes against humanity” will probably not help his relationship with the United States.

President Trump may not have flinched at praising Duterte’s drug war in a phone call, but other branches of the U.S. government might be persuaded to take a more public stand against alleged rights abuses if a “crimes against humanity” mention was thrown into every news account of what is happening in the Philippines.

“It is unfortunate that it has not acted sooner because, of course, that fact would have been part of the story when it was revealed what Trump said to Duterte,” Whiting, the former ICC prosecutor, said.

“It's not that it would have necessarily made a difference to Trump himself,” he added, “but it would serve as an important marker and signal that it would matter to many U.S. allies who are members of the court.”

Kimberly dela Cruz contributed to this report.