How is suspected Pennsylvania trooper killer Eric Frein surviving?

CANADENSIS, Pa. - It's day 12 of the manhunt for accused state trooper killer Eric Frein.

He remains on the FBI's 10 most wanted list for the deadly ambush of the Pennsylvania state police barracks.

The self-taught survivalist could be taking full advantage of his skills to stay one step ahead, reports CBS News correspondent Vladimir Duthiers.

Tom Brown Jr., a survival expert and tracker, demonstrated for CBS News what Frein might be doing to endure the elements and showed how police can find him.

"What the police try to do is to get into the mind of the person they are tracking," said Brown.

Brown has close to 35 years experience in tracking and wilderness survival techniques.

The 2003 movie "The Hunted" starring Tommy Lee Jones and Benicio Del Toro was loosely based on one of his cases.

He's helped law enforcement track down dozens of criminals on the run. He can spot even the tiniest footprints, like that of a mouse.

A few miles from the forest where Brown demonstrated his skills, state troopers are working with trackers to search for Eric Frein deep in Pennsylvania backcountry.

"He's either vacated the area, or he's got some kind of a bunker there, you know built in a cave," said Brown.

Law enforcement have said they're closing in on Frein's trail.

"I know the kinds of sweeps and things we're doing; there's no doubt we are pushing him hard," Lt.Col. George Bivens said in a press conference on Sunday.

Why can't police just go and capture him?

"You can't, that would be suicide," said Brown. "Let's face it, if you and I were standing here, and we knew a guy had a shelter up there, but he's also has a high powered rifle, he's got a clear shot on us, everything has to be done slowly."

That may be why the police haven't stormed his position.

"If they find his stash, it's going to be trip wired," Brown said. "When it comes near the end, it's going to be a firefight."

Brown told CBS News' that Frein's supplies will eventually run out.

While he's not officially helping the Pennsylvania police on this case, he is confident that law enforcement will find Frein, one way or another.