Fallen South African athletic star Oscar Pistorius will rely on a hand-picked team of forensic experts when he mounts his defence against murder charges at a trial beginning Monday.

"We are going to see a clash of experts in this case. It is going to be an issue of how the forensics plays out," according to David Klatzow, a South African forensic scientist not linked to the case.

Pistorius, the 27-year-old Paralympian and Olympian dubbed the "Blade Runner" for his prosthetic legs, is on trial for the premeditated murder of his model girlfriend Reeva Steenkamp, whom he shot dead on Valentine's Day 2013.

He is expected to argue he shot his 29-year-old lover through a locked toilet door at his home believing she was an intruder.

The prosecution will use forensics to show that, far from being scared, Pistorius fired at Steenkamp from a close distance, repeatedly and with premeditation.

"The precise positions at which the shots were fired; the grouping of the shots; the number of shots that were fired," are among the key points to be raked over by experts according to Klatzow.

"Ballistic evidence is going to show that Oscar was very close to the door and that is going to be a difficult thing, I think, for him to explain away."

"It doesn't make sense to approach the danger more closely," said Klatzow.

"His next problem is he fired so many shots," he added. "He will have difficulty justifying the reasonableness of firing four shots."

- 'A question of resources' -

To address those problems, Pistorius will call on at least four forensic scientists, ranging in expertise from guns to blood splatter, to testify in his defence.

The all South African forensic team includes forensic geologist Roger Dixon, private forensic pathologist Reggie Perumal, and gun experts Thomas Wolmarans and Jannie van der Westhuizen.

Team Pistorius is unusual for its size and depth in South Africa, a country with a 25 percent unemployment rate where the average annual income is around $9,500 (7000 euro).

"It's a question of resources," said Stephen Tuson, criminal law adjunct professor at the University of Witwatersrand in Johannesburg.

"Many trials are run with the barest minimum of forensic evidence, a post-mortem report by the pathologist and maybe a few photographs."

All the experts, except Perumal, are based in Pretoria, where Pistorius has lived with his uncle, businessman Arnold Pistorius, in preparation of the trial.

It makes sense that Pistorius hired people from his own country, said Michael Baden, a forensic expert speaking from New York.

"In my experience, the local experts are given more credibility by judges... than someone who could be called a carpet bagger or hired gun," said Baden, author of "Dead Reckoning: The New Science of Catching Killers."

But Pistorius also looked overseas for help.

- Send in the cavalry -

Pistorius has also hired The Evidence Room, an American forensic animation firm based in Cleveland, Ohio, to digitally recreate the crime scene using computer animation, a craft popularized in movies such as Toy Story and Shrek.

"It's basically a virtual environment, it's just such a great way of explaining things," says Brian Brill, manager at Mountain Graphix, a forensic animation firm in Dillon, Colorado.

Brill, who used to be a ski patroller before animating accident scenes, said he usually charges around $200 an hour.

The price tag for complicated cases can run as high as $20,000, he said. But the 46-year-old said the video evidence is priceless.

"A picture is a thousand words, so basically an animation is a thousand pictures," he said, "it's great for explaining the lay of the land."

Pistorius's investment may well be a shrewd one, according to Klatzow.

"I am hoping that it does not turn out to be a case of duelling experts. But all too often this is what happens."

"You have the state expert who says categorically black, you have go the defence expert who says categorically white. It ends up as often highly technical duel."

"What often happens unfortunately is the judge ends up weighing experts rather than experts' testimony."