(CNN) -- Supermodel Naomi Campbell took the stand Thursday in the trial of former Liberian President Charles Taylor and said she received a gift of "dirty-looking stones" that she assumed was from him.
Campbell was handed the stones following a dinner hosted by Nelson Mandela in 1997.
"When I was sleeping I had a knock on my door. I opened the door and two men were there. They gave me a pouch and said, "A gift for you.'"
The men didn't introduce themselves nor say anything else, Campbell said.
The next morning, she opened the pouch and saw a few "very small, dirty-looking stones."
She then shared what happened with her agent and another woman at breakfast.
"Well that's obviously Charles Taylor," one of them said.
Then, one of them added, "Well, obviously they are diamonds."
Taylor faces war crimes charges over a brutal conflict in Sierra Leone which was fueled by rough diamonds, also known as blood diamonds or conflict diamonds.
Prosecutors say Taylor gave Campbell a diamond during the war in Sierra Leone, contradicting Taylor's testimony that he never handled the precious stones that fueled the conflict.
The defense said it hadn't seen a copy of Campbell's testimony, which interferes with Taylor's right to a fair trial.
Under tribunal rules, the defense team should get advance access to prosecution witness testimony so it can prepare its arguments. Prosecutors said they have not obtained a statement from Campbell, but they did provide a copy of her anticipated testimony to the defense.
Prosecutors had rested their case against Taylor in February 2009, but reopened it specifically to call Campbell to testify after learning in June of that year that Taylor had given the supermodel a diamond in South Africa in 1997. Prosecutors said they also wanted to call actress Mia Farrow and a witness named Carole Taylor to testify, court papers show.
Prosecutors have said that Farrow confirmed that Taylor gave Campbell a diamond.
When arguing to reopen the case, prosecutors said Campbell's testimony would prove that the former president "used rough diamonds for personal enrichment and arms purchases," according to papers filed with the U.N.-backed court.
Campbell did not want to be involved in the trial but was subpoenaed July 1.
Taylor, 62, was president of Liberia from 1997 to 2003. The war crimes charges against him stem from the widespread murder, rape and mutilation that occurred during the civil war in Sierra Leone. It was fought largely by teenagers who were forced to kill, given addictive drugs to provoke violent behavior, and often instructed to rape and plunder.
Taylor is charged with five counts of crimes against humanity, including murder, sexual slavery and violence, and enslavement.
He also faces five counts of war crimes, including acts of terrorism and torture, and one count of other serious violations of international humanitarian law.
He has pleaded not guilty.
CNN's Lianne Turner contributed to this report