The British beauty took the stand at The Hague, Netherlands, over claims she accepted blood diamonds - illicit gem stones which are sold to finance conflicts - from former Liberian President Charles Taylor in 1997.
Campbell told the hearing a pouch of stones was delivered to her by two unknown men after a dinner party, and she did not consider the gift could have been from Taylor until the following morning, when actress Mia Farrow told her it was "obviously" from the politician.
At the close of her evidence on Thursday, Campbell denied an accusation that her account of the incident was untrue.
Prosecutor Brenda Hollis asked the model, "Isn't it correct that your account today isn't entirely truthful?"
Campbell replied, "No, that's not correct."
Taylor's defence lawyer, Courtenay Griffiths, objected to the line of questioning, and Miss Hollis did not pursue it.