Nearly four months after the murder of Jamal Khashoggi at the hands of Saudi operatives linked to the court of Crown Prince Mohammed bin Salman, the United Nations (UN) is launching an investigation into the killing of the journalist, potentially shining a new light on an explosive case.

Agnes Callamard, the UN’s special rapporteur on extrajudicial, summary or arbitrary executions, will travel to Istanbul on Monday to begin an examination of the murder. The 59-year-old Saudi journalist was abducted, brutalised, murdered and dismembered on the 2 October inside his own nation’s diplomatic facility in Istanbul during a routine consular visit.

Ms Callamard, director of Columbia University’s Global Freedom of Expression project and a former Amnesty International investigator, will be joined by Helena Kennedy, a UK barrister, and Duarte Nuno Vieira, a Portuguese forensic pathologist.

The team will assess the steps taken by Turkish and Saudi authorities to grapple with the case, as well as “the nature and extent” of responsibility for the crime by governments and individuals ahead of a June meeting of UN officials.

“The inquiry will also seek to identify ways by which states can strengthen fulfilment of their international commitments to protect the right to life, prevent violations and ensure accountability,” Ms Callamard said in a statement posted to the website of the UN’s human rights branch.

Amnesty, Human Rights Watch and other human rights and press freedom advocacy groups have long called for an independent international investigation into the Khashoggi murder. The suspects in the case flew back to Saudi Arabia hours after the killing, aboard private jets operated by a company linked to the Saudi leadership.

Saudi judicial authorities claim they are prosecuting 21 suspects in the killing, which they insist was a rogue operation ordered and carried out by senior officials close to Prince Mohammed, de facto ruler of the kingdom,

A longtime supporter of the Saudi system, Khashoggi fled into exile during the rise of Prince Mohammed and became a contributor to The Washington Post and a frequent guest on Arab-language television shows where he criticised the 33-year-old heir-to-throne.

Saudi authorities have barred independent international observers from attending court sessions amid rumours that some of those allegedly behind the killing were living freely. Turkish foreign minister Mevlut Cavusoglu, during a television interview on Thursday, welcomed an international inquiry into the Khashoggi affair, accusing countries of trying to cover up the murder to protect Prince Mohammed.

Many of the billionaires, world leaders and corporate kingpins at the World Economic Forum in Davos this week said they were ready to put the Khashoggi affair behind them, and resuming normal business with Riyadh. Saudi economy minister Mohammad Al Tuwaijri said he and his colleagues met with “dozens” of western investors.