As Afghan and Western troops close in on what they believe is Osama bin Laden's hideout in Tora Bora, they face a new challenge.

     How will they know if they have the right guy?

     In the three months since September 11, 44-year-old bin Laden could have done anything from escape to Yemen to having his physical appearance altered through plastic surgery. He also reportedly has a team of lookalikes who travel with him.

     But former intelligence and medical experts say the US Government has the means to identify its elusive target under almost any circumstances, dead or alive.

     "I'm sure they have fingerprints, they certainly have pictures and they probably have DNA if they need it," said Frederick Rustmann, a former CIA counterterrorism expert.

     ABC News reported that the US had obtained DNA samples from bin Laden's family. Bin Laden, whose father had 54 children, has relatives in the US who could have provided DNA samples.

     Yet the primary means of identification will be less hi-tech.

     "He'd love to become shorter, I'm sure," said Mr Rustmann. "I just hope they arrest anyone crossing the Afghan border over six feet tall."

     Standing at about 1.9 to two metres tall, bin Laden is head and shoulders above most of his Afghan followers.

     Mr. Rustmann said any intelligence profile of bin Laden would also include all vital physical statistics. Bin Laden, for instance, is believed to require dialysis for kidney failure and to have heart trouble.

     Mr. Rustmann has no doubt the US will find bin Laden or his body, no matter where he's hiding or what he looks like. He believes that if he is found alive, the orders will be to shoot first and ask for passports later.