The Special Court for Sierra Leone says it will allow prosecutors to call supermodel Naomi Campbell to testify about a "blood diamond" she was allegedly given by former Liberian president Charles Taylor.

Actress Mia Farrow can also be called to give evidence on claims that Ms Campbell was given the rough diamond by Mr Taylor after a dinner hosted by former South African president Nelson Mandela in September 1997. Prosecutors filed the request in May, seeking permission to call Ms Campbell, Ms Farrow, and the model's former agent, Carole White.

Ms Campbell has so far refused to give evidence on the matter, but Ms Farrow and Ms White, both present at the dinner, are willing to do so, according to the prosecution's submission. On Wednesday, a court spokesman said the prosecution was awaiting the outcome of a separate application for a subpoena, compelling Ms Campbell to appear.

Prosecutors say that Ms White was present when the diamond was delivered, while Ms Farrow "was told by Ms Campbell the next morning about the gift". According to a declaration, Ms Campbell said that “she had been awakened in the night by knocking at her door. She opened the door to find two or three men, she does not recall how many, who presented her with a large diamond which they said was from Charles Taylor."

The prosecution alleges the rough diamond was among those Mr Taylor had obtained from Sierra Leone rebels and taken to South Africa "to sell [...] or exchange for weapons". Mr Taylor, 62, has been on trial in The Hague since January 2008 on 11 counts of war crimes and crimes against humanity stemming from the 1991-2001 civil war in Sierra Leone.

He is accused of having fuelled the war by arming the rebel Revolutionary United Front (RUF) in exchange for ‘blood diamonds’, diamonds mined in rebel-held regions of Africa and sold to fund warfare. The RUF is blamed for mutilation of thousands of civilians who had their hands and arms chopped off. Sierra Leone’s civil war was one of the most brutal in modern history and claimed some 120,000 lives.

Prosecutors say they did not know about Ms Campbell’s diamond, which they consider material evidence in the case, until June 2009. By that time, they had already closed their case. At the moment, defence witnesses are being heard.

Mr Taylor has opposed the bid to reopen the prosecution case and call the women, saying the evidence in question was "more appropriate for a screen-play than a courtroom hearing". But a panel of four judges, having studied Ms Farrow's declaration and notes of an interview with Ms White, have now ruled that the new evidence is “highly probative". The prosecution will be allowed to reopen its case and call the three to the stand before the last defence witness who are expected to be heard in August.