Because cartels accumulate houses full of cash, they run the constant risk associates will skim off the top. That points to the main reason cartels prefer their own people: Trust is hard to come by in their cutthroat world. There's also a fear factor. Cartels can exert more control on their operatives than on middlemen, often by threatening to torture or kill loved ones back home.
Danny Porter, chief prosecutor in Gwinnett County, Ga., said he has tried to entice dozens of suspected cartel members to cooperate with American authorities. Nearly all declined. Some laughed in his face.
"They say, 'We are more scared of them (the cartels) than we are of you. We talk and they'll boil our family in acid,'" Porter said. "Their families are essentially hostages."
Citing the safety of his own family, Gonzalez-Zavala declined to cooperate with authorities in exchange for years being shaved off his 40-year sentence.
In other cases, cartel brass send their own family members to the U.S.
"They're sometimes married or related to people in the cartels," Porter said. "They don't hire casual labor." So meticulous have cartels become that some even have operatives fill out job applications before being dispatched to the U.S., Riley added.
In Mexico, the cartels are known for a staggering number of killings — more than 50,000, according to one tally. Beheadings are sometimes a signature.
So far, cartels don't appear to be directly responsible for large numbers of slayings in the United States, though the Texas Department of Public Safety reported 22 killings and five kidnappings in Texas at the hands of Mexican cartels from 2010 through mid- 2011.
Still, police worry that increased cartel activity could fuel heightened violence.
In Chicago, the police commander who oversees narcotics investigations, James O'Grady, said street-gang disputes over turf account for most of the city's uptick in murders last year, when slayings topped 500 for the first time since 2008. Although the cartels aren't dictating the territorial wars, they are the source of drugs.
Riley's assessment is stark: He argues that the cartels should be seen as an underlying cause of Chicago's disturbingly high murder rate.
"They are the puppeteers," he said. "Maybe the shooter didn't know and maybe the victim didn't know that. But if you follow it down the line, the cartels are ultimately responsible."
Follow Michael Tarm at www.twitter.com/mtarm .
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