Inside our border's first line of defense

At the port of Los Angeles, something has triggered the alarm.

Officer Keith Labranche: We're going to go out there right now and grab the driver's information and container number.

Officer Keith Labranche knows that means there is some kind of radioactive material in the back of this truck. He's on the lookout for any threat to the nation's security.

Labranche: Anything that could be used to make a dirty bomb, or poison something--water supply, food sources--anything like that.

Labranche walks around front to the driver's window.

Labranche: Have your license? Thank you sir. When the gate arm pulls up, just pull forward to customs secondary. Thank you.

Labranche: We're going to conduct a radiation screening first. The container had a pretty significant spike in terms of radiation readings so we're going to run the container through our targeting system and see what we have for commodity.

Officers access the shipping list:

Ryan: Grinders, polishers and sanders, coming from China.

Sounds harmless enough, but there's only one way to find out. After a second screening with a handheld radiation detection device, he's going in.

Labranche: I’m going to go ahead and open the container to verify the commodity.

Labranche: You want to look for duffel bags, you want to look for holes in a container where maybe someone could come on inside the container, open it up, and pull out a single box, anything that may have a smell, anything that might be leaking.

Labranche: I’m going to open it up. Looks like an air ratchet used to attach the grinding wheels that we have listed inside.

The cargo checks out. No dirty bombs or terrorist weapons. Some imported items, like granite counter-tops, TV sets and those tools from China give off trace amounts of natural radiation which can trip the alarm.

Labranche: The final finding is it's normal, everything's consistent. Radiation matches up with the type of commodity inside so it's OK to let go.

Officer Labranche can stand down, but not for long. Some days the seaport's alarm goes off 600 times.

Labranche: It sounds pretty clichéd, but it just takes that one container to get in the U.S. somehow and anything could be in it and every can has to be screened.

Wheels of fortune
In Texas, CBP officers face other potential threats to the border.

Lopez: The port of El Paso is the second largest port on the southern border. Every day we process over a 100,000 people. And we process on an average about 40,000 vehicles.

Lopez: Our primary mission is antiterrorism and along with that mission we conduct all these other inspections we come across narcotics.

Chief CBP Officer Rick Lopez, uniform liaison (17 years on the job): It could from 8 up to 15 seizures a day. Come out here, talk to them, are they nervous, are they not? Where are they going? Picking up on some of the clues that maybe might lead to illegal activity. Picking up on some of these what I refer to as indicators, where an applicant comes in, he's grabbing the steering wheel, his knuckles white. It's hot as hell this evening. A grey Mercury Marquis has entered the checkpoint. It looks clean. Maybe too clean.

Lopez: The officer is doing a lot of interacting with the driver of the vehicle.

No high-tech tools here. The officer relies on experience and a basic, but powerful weapon in the war against drugs.

Jazz is a CBP detector dog, a German shepherd who’s been on the job for 13 months.

Officer Brenda Rubio, canine officer (6 years on the job): Jazz and I have been working together since July of 2007. She smells marijuana, hash, cocaine, heroin, ecstasy and meth.

Rubio: Their noses are 10,000 times stronger than ours. The inspector called me over to this lane, he felt there were some inconsistencies.

Jazz is trained to alert her handler when she finds drugs. She does it by sitting down immediately.

Rubio: What I do, I just walk around the vehicle with Jazz. She alerted to the rear tire. There's a hit. Soon officers will find out if Jazz is right.

Out of darkness
The Sonoran desert is a sea of sand that spans from the southwestern U.S. to northern Mexico.

Pilot: This evening we're about to go on a patrol along the border between Arizona and Mexico in support of the United States Border Patrol, Tucson sector. We're just going to be looking for any illegal activity, and any requests for air support from search and rescue to vehicle pursuit. Anything could happen really.

There are no natural barriers separating the two countries, and few manmade ones.

Pilot: In an eight-hour shift, we encounter just about everything. Predominately it's of a human smuggling nature or narcotics smuggling.

To monitor this vast unpopulated frontier, the border patrol has immersed itself in technology like it was water in the desert.

Their arsenal now includes GPS, night vision, surveillance cameras, listening posts, and ground sensors.

Lee Albee, supervisory agent, mobile surveillance system operator (12 years on the job): The technology allows us to find the traffic as it comes across the border. This equipment is looking at wide swaths of the desert floor. And whereas it would perhaps take 10 to 15 agents to cover all this area on foot, we can cover the same amount of area with one of these pieces of equipment.

Six hours later, agent Lee Albee’s sensors get a hit. He radios a jeep patrol.

Radio: Keep going as quiet as you can. They're about three quarters of a mile south on that road.

Agent in jeep: Well, what we know is that there's a small group of three that are moving at a pretty quick pace.

Agent Joe Gonzalez: It looks like in addition to us, we've got a two-man unit in front of us that's going to be helping us out.

The jeep patrol closes in with the help of agent Albee’s GPS coordinates.

Radio1: I’ll give you numbers to line you up.

Radio2: 10-4. Send the grids.

Radio1: 31, 42.972. West is 111. 44.590. You guys are on the right road, just keep going.

As the agents close in, the sensors lose contact.

Agent Joe Gonzalez: The mobile surveillance system was able to track them to a real thick, brushy area and after that it couldn't get a signal.

Agent Joe Gonzalez: Right now, he's looking for footprints.

Agent Joe Gonzalez: 10 percent of the individuals we encounter in Tucson sector have previous criminal histories somewhere in the U.S. That's convictions ranging from shoplifting to multiple homicides, so we don't know who we're going to encounter.

About 30 minutes later, border patrol agents find them. Three men attempting to sneak into the country, one of whom has a warrant out for his arrest.

Agent Joe Gonzalez: The agents were able to get there, find the footprints, and follow the footprints to where the subjects were hiding.

A few miles away, sensors detect yet another group crossing the desert.

Agent: A group of five individuals, carrying large backpacks.

The chase is on.

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