More than 40 people convicted in such stings could go free if a special nine-judge panel eventually rules that discrimination underpins the stings. The operations run by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives typically involve agents posing as cartel couriers who talk suspects into agreeing to rob drugs that don't exist from stash houses that are also fictitious.
While the same question has come up in courts elsewhere, it is the federal trial judges in Chicago who have taken the lead in seeking an answer. And how they decide the sensitive and complex issue could determine if agencies curtail or even abandon their use nationwide.
The answer to whether the stings do or don't discriminate based on race largely hinges on competing interpretations of statistics.
Jeffrey Fagan, a defense expert who took the stand first, testified that data clearly shows blacks, and in some cases Hispanics, are disproportionately singled out for the stings. Government witness Max Schanzenbach argued later that Fagan's methodology was flawed.
One panelist, Judge Robert Gettleman, sounded doubtful that competing stats can decide the question. Highlighting the unreliability of statistics, he referred to Mark Twain's quip about three kinds of lies: "Lies, damned, lies and statistics."
The judges on the panel each presides over 12 separate stash-house cases with 43 defendants, a dozen of whom sat Thursday in a jury box. Some yawned or sank in their seats as testimony strayed into math, and technical explanations about probabilities.
The judges chose to hear evidence simultaneously after lawyers for all 43 defendants moved for the stash-house charges to be tossed on grounds of racial bias. How they decide - possibly in a single ruling - is expected to influence how courts nationwide deal with similar claims.
Among the panelists who were scheduled to hear a second day of testimony Friday is Ruben Castillo. His ruling in 2013 that there's a "strong showing of potential bias" in the stings generated years of legal motions and dueling expert reports - culminating in this week's hearings. Castillo is the Chicago federal court's first Hispanic chief judge.
Courts have ruled previously that proving racial bias doesn't necessarily require proof of explicit racist behavior, such as an official caught using racial slurs. It can sometimes be enough to point to statistical evidence that a racial group is disproportionately hurt by a policy.
Fagan noted that out of 94 stash-house defendants in the Chicago area between 2006 and 2013, 74 were black, 12 were Hispanic and just eight were white. If the ATF criteria for picking targets were truly colorblind, he said, far more whites would have been snared.
But government lawyers have argued it's only natural that trafficking-related stings are focused where trafficking activity is highest - in low-income areas on Chicago's South and West Sides.
And their expert testifying Thursday said Fagan was wrong to assume in his analysis that hundreds of thousands of people in eight counties in and around Chicago would be willing to entertain the idea of arming themselves and storming a stash-house. He said that assumption skewed Fagan's findings that the 43 defendants, many of whom with convictions of violent crimes, were unfairly singled out.
The stings have been criticized on other grounds, including for agents' power to arbitrarily increase the severity of charges simply by increasing the amount of non-existent drugs they tell targets are in the non-existent stash houses. Suspects can also be charged with trying to distribute the phantom drugs, charges that carry stiff mandatory prison terms.
"The time has come to remind the Executive Branch that the Constitution charges it with law enforcement - not crime creation," a U.S. judge in central California, Otis Wright, wrote in a scathing 2014 ruling.
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