The youth, a software engineer, who has been deposing before the court for the last two days was not present on Thursday.
He is the sole eyewitness to the brutal assault and gangrape of the 23-year-old girl, who can not be named due to legal reasons.
The doctors of the Safdarjung Hospital here have been called by the court on Friday for recording their evidence.
The 28-year-old victim's friend, who is chief prosecution witness had testified before the Additional Sessions Judge Yogesh Khanna in an in-camera proceedings against the five accused, who have pleaded not guilty to charges, including rape and murder, framed against them.
The details of the proceedings cannot be reported by the media as the court has imposed a ban on it under the provisions of the Indian Penal Code.