Statistical Quandary: Mass Killings in Cities’ Homicide Counts


Before last Monday's mass killing at the Navy Yard, Washington, D.C.’s homicide count was about on pace with 2012, a year that ended with 88 slayings, the fewest in a half-century. A lone gunman who opened fire in one building has made it unlikely that the city will count record low homicides again this year, says the Washington Post. Police Chief Cathy Lanier added the 12 Navy Yard slayings to the crime statistics but added an asterisk marking them as an exceptional tragedy. The city's homicide count jumped 28 percent. As more cities join the grim list of those that have experienced mass-casualty attacks, authorities are struggling with how to record them for statistical purposes and present them to the public in proper context.

Authorities in Aurora, Colo., held meetings filled with soul searching to come up with a way to record last year's killings of 12 patrons at a movie theater. They listed the total number of homicides at 29 — including those who were killed in the mass shooting — but also put a number 12 in parentheses next to the total. In an annual report, police explained that the victims claimed by one gunman turned what would have been a 3.5 percent drop in violent crime into a 1.9 percent increase. “We didn't want our tragedy to be a reflection of our crime rate,” said Sgt. Cassidee Carlson of the Aurora Police Department. “It's very clear that what happened is not typical. Obviously, it needed to be reflected. It happened. But we wanted to be smart about how we reflect what happens in our city.” Criminologist James Alan Fox of Northeastern University said crime statistics are used “as a barometer of safety and of police performance” and said mass shootings should not be left out.

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