The Border Patrol has been experimenting with airborne radar to count getaways. A trial run in a 150-square-mile stretch of Arizona found about 1,870 were caught and about 1,960 got away from Oct. 1 through Jan. 17, according to a senior Customs and Border Protection official who spoke on condition of anonymity because results have not been made public.
U.S. authorities play down the significance of the radar results, first reported by the Los Angeles Times, saying the technology is promising but flawed.
For now, sign-cutting is the main tool.
Gordon seems to find clues everywhere: a pebble with moist dirt facing the sun to suggest it was recently overturned; backpack fibers stuck on a barbed wire fence; fallen leaves. In off-hours, he looks for clues about how many people stepped on his driveway or came before him on a walking trail.
He examines each sign to determine its age. He knows a cloverleaf curls immediately after it falls. He can tell how quickly a trampled blade of grass returns to its natural height and how fast a broken tree limb turns brittle.
Around the clock, agents lay fresh tire tracks on dirt roads that hug the border, recording the times to help determine the age of each new set of footprints.
Smugglers have become adept at covering their tracks, ordering migrants to tie blankets over the soles of their shoes to avoid leaving sharp footprints. The last person in the group may carry a jug of dirt to sprinkle over any traces. Some migrants walk backward to leave an impression that they turned back to Mexico. At night, migrants walk on paved roads to avoid leaving prints, a trick called "blacktopping."
The best hours to track are early morning, when sunlight casts a long shadow, and under a flashlight's evening glare.
Gordon began patrolling a highway checkpoint in Southern California in 1990 and, seven years later, transferred to Campo, where his father also gained a reputation as an expert Border Patrol tracker. Unlike urban stretches of the 1,954-mile border with Mexico that are crowded with houses, agents must learn quickly to read tracks in the parched, desolate valleys of oak and shrub.
Gordon, who is still fit enough to hustle through thick brush with his chest pressed to the ground, is second-in-command in a station that employs about 400 agents to scour 400 square miles. He captured a group of 76 when illegal crossings near the station peaked about 10 years ago. Until about five years ago, the station often made 100 arrests a day.
Illegal crossings slowed to a trickle since the Border Patrol responded to the 2009 assassination of a Campo-based agent by flooding the area with agents and cameras. It isn't unusual for the station to go shifts without making any arrests, a luxury the station chief says has allowed agents to pursue groups of only two or three people over days and sharpen their tracking skills.
When someone is captured, agents scour the area in widening circles until they feel confident that they caught everyone in the group or know how many got away. One obvious sign of a getaway is when a set of footprints ends in a well-known staging area for smugglers to pick up migrants in cars.
When migrants are caught, a supervisor typically makes the call on when to count a getaway. "There is nothing scientific about this," Gordon says. "Some people are better at it than others."
Associated Press writer Alicia Caldwell in Washington contributed to this report.
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