With his murder trial approaching this March, South African Olympic runner Oscar Pistorius has hired some help from the United States to challenge the case against him.

An American forensic team will give expert testimony to cast doubt on evidence entered against the athlete nicknamed the "blade runner" for the special prosthesis legs he sprints with, his spokeswoman Anneliese Burgess said Wednesday.

The track star, whose legs are amputated below the knees, admitted to shooting dead model Reeva Steenkamp, in his home on Valetine's Day. But he has said it was an accident.

She was 29 when she died.

The state has indicted him for pre-meditated murder, and he faces a mandatory sentence of life in prison, if convicted.

Pistorius denies the charge and has said he mistook his girlfriend for a home invader when he fired shots from a pistol through a bathroom door that she was behind. Pistorius also was indicted for allegedly violating South Africa's firearms control act. Some 107 witnesses are to testify against him.

The American forensics team, who Burgess would not identify, is already in South Africa and has met with Pistorius' legal team.

In previous court appearances, Pistorius has often broken down crying and fought to maintain his composure. Before the start of proceedings he could be seen at times holding hands with relatives and praying.

CNN's Joseph Netto contributed to this report