The prosecution also relied on accounts of alleged accomplices and migrants who entered the country illegally, including some who identified Fidel Villarreal in photographs. One 24-year-old Brazilian woman said she paid $12,000 to be taken across the border in "a police car."

Prosecutors said the brothers were tipped off about the investigation in June 2006, prompting them to flee to Mexico.

Shortly after they settled in Tijuana, a district police commander in the Mexican border city who allegedly shuttled Villarreals' customers in squad cars was killed in a hail of about 200 bullets. The brothers were arrested in October 2008 — more than two years after abruptly quitting the Border Patrol — and extradited to the U.S. to face federal charges of human smuggling, witness tampering and bribery.