There have been some alarming headlines recently about how murder is on the rise in cities across America. Suggesting that sharp homicide increases in Milwaukee, Baltimore, St. Louis and other urban jurisdictions may point to a national trend, some coverage pointed to a possible “Ferguson effect.” That’s the theory that police have become overly cautious in the wake of protests.

In this week’s podcast, ProPublica reporters Alec MacGillis, Lois Beckett and Ryan Gabrielson talked about what we really know about the murder rate and what is driving it. They explain the need for caution when talking about violent crime data – and the problems of trying to analyze it in real time.

Photo: Police officers in riot gear hold a line as they watch demonstrators protest the shooting death of Michael Brown. (Joshua Lott/AFP/Getty)

Some highlights from their discussion:

  • When it comes to explaining shifts in violent crime, everyone is just guessing. Citing reasons that experts have given for the past two decades’ historic drop in crime (including more police forces, less lead paint on houses, and the legalization of abortion) Gabrielson said no theory fully explains the decrease. “That should bring about a lot of caution and humility in trying to ascribe what’s going on now to any motive or phenomenon,” he said. (1:50)

  • Data doesn’t support the “Ferguson effect” theory. Beckett pointed out that St. Louis’ 2014 homicide surge started before Mike Brown was killed. But even a city like Baltimore, which saw a spike in homicide after Freddie Gray’s death, has unique conditions and a distinct police department that can’t be equated to others. “A lot of rhetoric and political grandstanding around homicide stats cherry-pick all of these very different local problems and try to unite them all under the premise that the police are in retreat,” she said. (4:54)

  • But police violence and homicide rates don’t have to be discussed separately. MacGillis, who lives in Baltimore, said many people he’s spoken with have a nuanced view that draws connections between the lack of community trust in black neighborhoods and high murder rates. “Excessive police misconduct matters very much, but what also matters is police inability to address the homicide problem,” he said, seeing them as two sides of one coin. (8:46)

Listen to this podcast on iTunes, SoundCloud or Stitcher. For more data reporting on policing, read Deadly Force, in Black and White.