The U.S. Justice Department plans to collect data in five pilot cities on police stops, searches, arrests and case outcomes in a bid to ferret out the “possible effect of bias within the criminal justice system,” says the Washington Post. The effort is part of the new National Center for Building Community Trust and Justice. The data may be exceptionally difficult to obtain. Perhaps you think you’ve already seen something like it. Attorney General Eric Holder quoted a study finding that by the age of 23, it found, half of black men have been arrested at least once. Similar data suggest that black men are six times more likely to be incarcerated than white men. Such data don’t tell us much about police bias, about whether those disparities exist at least in part because officers on the street are stopping and arresting black men more often than whites for no reason other than their race. The question is not whether minorities are stopped at a higher proportion than their share of the local population would suggest but if they’re stopped in higher proportions than the rate at which they commit crime.
“What you'd want to know is this: Since African-Americans are six times more likely to be stopped and frisked, are they six times more likely to be in possession of something criminal when they're stopped?” says John Roman of the Urban Institute’s Justice Policy Center. If you were to stop people on the streets of New York entirely at random, would that be true? This is a particularly difficult question to answer because we are trying to compare stop and arrest rates (about which we have data) with criminal behavior (about which we seldom do). We know, for instance, who and how many people are arrested and convicted within a given year in any city for burglary. But we don’t know how many people — or which people — in that city committed a burglary, with or without getting caught. That larger group by definition evades data.