Due north

BLAINE, Wash.- As two armed murder suspects raced north on Interstate-5 toward the U.S.-Canada border Jan. 24, about 20 unarmed Canadian border guards fled for safety. The pair of criminals accelerated up to 100 mph, plowing over a spike strip and through a border checkpoint before crashing into Peace Arch Park.

A Whatcom County, Wash., sheriff's deputy blocked the speeding vehicle with his squad car, and a U.S. Customs and Border Patrol agent fired his gun, wounding Ishtiaq Hussain of Pakistan. U.S. agents arrested Mr. Hussain, 38, and Jose Antonio Barajas, 22, of Mexico.

Canadian officials insisted that, despite their agents' actions, security was never compromised. But the stark contrast between fleeing Canadians and unflinching American gunslingers speaks volumes about the current state of border protection-and the differing approaches the two North American neighbors have employed since 9/11.

Two weeks after the terrorist attacks on the Pentagon and World Trade Center, Robert C. Bonner took over the U.S. Customs Service and transformed it into a homeland security agency. The newly formed U.S. Customs and Border Protection underwent a dramatic shift in primary focus-from fruit flies, drug smugglers, and desperate workers to chemical weapons and the terrorists who wield them.

Federal dollars, new technologies, and extra manpower have since poured into the border-protection effort. This past December, Congress passed the Border Protection, Antiterrorism and Illegal Immigration Control Act, a plan to increase border canine teams, establish a new felony dubbed "illegal presence," and build 700 miles of multilayered, high-tech fence between the United States and Mexico.

Such efforts to quell the thousands of illegal immigrants crossing the U.S.-Mexico border each day should help quiet the perpetual drone of grumbling about border security that has plagued the Bush administration. But no amount of southward attention will silence concern over the much-less-trafficked border to the north. Every known al-Qaeda operative captured at a land border crossing in the last several years has sought entry from Canada.

Canada's generous welfare program, lax immigration policies, and high Muslim immigrant population provide an ideal nesting ground for terrorist cells. Despite the threat, the United States has no intention of erecting any fences along the Canadian border. The commitment of both nations to maintain the public perception of an open and friendly relationship precludes it. Thanks mostly to improved technology, however, the border is more scrutinized.

Kenneth Williams, Customs chief of cargo operations at Blaine, ducked his head into a shelter adjacent to the Pacific Highway truck crossing last month and surveyed the wealth of high-tech gear stashed inside. Positioned near a window overlooking the port's gamma ray scanner, a computer monitor slowly rendered an X-ray-like image of the semitrailer parked outside.

As the cargo container came into view, inspectors noticed an anomalous lump near the rear of the bed. Having received the driver's radio message an hour earlier to expect a shipment of metal doors, officers elected to take a closer look. This time, the anomaly proved harmless-carelessly stored hockey bags filled only with hockey gear.

Since implementing the gamma ray imaging system, agents in Blaine and a host of other truck crossings have detected everything from undeclared merchandise to heaping loads of illegal narcotics. "Technology has helped us a lot," said Jay Brandt, the area's assistant port director. "I always wonder if people are getting through. That's the nature of thinking like a customs inspector. But I think we're safer than we were by a significant margin."

Mr. Brandt admits the limitations of even the latest technology. It can't perceive discomfort or identify odd behavior. For that, experienced inspectors remain irreplaceable.

Sophia Lopez has worked a noncommercial lane at the Blaine crossing for two years, developing an intuition for discontinuity. She compares her ability to the skills countless couples employ in picking up each others' moods-a verbal signal here, a misplaced word there. "It could be they're nervous. It could be they don't want to look you in the eye," said Lynn Gardner, Blaine's assistant deputy director for tactical operations. "That's the biggest thing about having good officers out there; they have a sense. It's almost like a sixth sense where they just feel something's wrong."

Officers need no legal justification to recommend a closer examination of a vehicle. Inspectors, in turn, are free to search whom they will. "People that come across the border are subject to search," said public affairs officer Mike Milne. "There's no probable cause needed."

Of course, with national security potentially hanging in the balance and the pressure of making a determination in less than a minute to keep the line of cars moving, the human system remains less than perfect. Between 6,000 and 7,000 vehicles pass through Blaine's two ports daily-the most traffic for any crossing west of Detroit. Of those, only 50 to 60 face a secondary inspection for reason of suspicion. "If we had more people, we could do more," Mr. Brandt said.

But the need for increased manpower at vehicle crossings pales to that in the wide-open spaces between the ports of entry. Stretched across 5,000 miles of varied terrain, a network of cameras, sensors, vigilant residents, and veteran officers forms an invisible fence. This mission is impossible-and one where rookies are not allowed.

All U.S.-Canada border patrol officers first sharpen their skills in the hectic and chaotic environment of the U.S.-Mexico border. Protecting a much broader national boundary to the north with a fraction of the agents requires the measured calculations and expert efficiency of experience. Cameras and sensors help, too.

"The more technologies we can get out there, the better our personnel can monitor what's going on," said assistant chief patrol agent Wes Vanderheyden. When Mr. Vanderheyden began patrolling this border in 1992 it was a challenge, he said. "We didn't have a lot of sensors, we didn't have a lot of manpower, and we didn't have any cameras."

Now footstep sensors monitor trails through wooded areas, and cameras perched atop roadside poles record images of open fields. Stepping across the border may not be simple, but there are points of vulnerability, sections where Boundary Road on the U.S. side and Zero Avenue on the Canadian side run parallel with only a 3-foot ditch between them. Opportunities to hurl drugs, weapons, or chemicals from one passing truck to another are unending.

"Have I ever, right here in Blaine, seen somebody carry in chemical or biological agents? No, but then again before 9/11, I never saw anybody fly an airplane into a building," Mr. Vanderheyden said. "We have to do as we can. There's not unlimited money."

Field operations supervisor Bob Kohlman pulled his squad car onto a gravel-and-dirt driveway off Boundary Road several miles east of Blaine. The 18-year border patrol veteran stepped out to the overpowering smell of nearby dairy farms. "It went right through here," he said, motioning toward a patch of pine needles and scrub brush beneath which a 360-foot-long tunnel lay before authorities filled it with concrete last summer.

The tunnel, which stretched from the living room of an inconspicuous tree-shaded residence on the U.S. side to a Quonset hut on the Canadian side, was the first subterranean passageway discovered between the two countries. Canadian officers received a tip as to the sophisticated structure's whereabouts before it was complete and contacted U.S. authorities. Three men were arrested and charged in Seattle's U.S. District Court with conspiracy to distribute and import marijuana.

The successful capture both reassured and concerned border guards, who wondered between high-fives whether terrorists with greater time and resources might enact a similar plan with different results. Since the 1999 arrest of "Millennium Bomber" Ahmed Ressam at a crossing in Port Angeles, Wash., border agents in the Northwest remain wary of the area's susceptibility to terrorist entry. Mr. Ressam, an al-Qaeda operative, planned to bomb Los Angeles International Airport on New Year's Eve.

Bittersweet sentiments shroud all such high-profile border captures, bringing confidence in a job well done but confirming fears that the danger is real. "The threat could come from anywhere," said Mr. Kohlman.