On murder clearance rates and fuzzy math

February 20, 2012|By Justin Fenton, The Baltimore Sun

In D.C., Chief Cathy L. Lanier is getting some heat for what the Washington Post reports is a "statistical mishmash" regarding the Metropolitan Police Department's sparkling homicide clearance rate of 94 percent of its 108 killings. As it turns out, many of the closed cases are from previous years:

In Baltimore, this revelation is not new or surprising, but it's worth reminding the public how the process works. First, here's some snippets from the Post article:

A 94 percent closure rate would mean that detectives solved 102 of them. But only 62 were solved as of year’s end, for a true closure rate of 57 percent, according to records reviewed by The Post.

D.C. police achieved the high closure rate last year by including about 40 cases from other years that were closed in 2011.

W. Louis Hennessy, a former D.C. police captain who oversaw the homicide unit from 1993 to 1995, called such statistics “entirely unfair.”

“They’re fostering the false perception that they’ve accomplished something when actually what they’re doing is fudging their numbers,” said James Trainum, a longtime D.C. homicide detective who handled several high-profile cases.

Trainum said homicide closure rates are a political football in the District. “Careers rise and fall based on statistics,” said Trainum, who also investigated cold cases before retiring in 2010.

Each year, when police close cases, they count the closure for the year in which they it was solved. The main reason for this, as it's been explained to me, is this: statistics, including clearance rates, are submitted each year to the FBI's Uniform Crime Reporting program, and if departments were to count the closure for the year in which the killing happened, they would be frequently revising each year's murder clearance rate. For example: if a killing from 1989 is solved this week, rather than reach back and revise the 1989 clearance rate, police tack it on to the current year. Is this misleading? Perhaps. But it doesn't seem any less misleading - or politically advantageous - than a murder from Dec. 31, 2010 that is solved on Jan. 1, 2011 counting for 2011 instead of burnishing 2010's murder clearance rate.

As a reporter who tracks these numbers almost daily, it makes sense to me to ask for the closure rate for the year to date including prior year cases, rather than asking for updated clearance rates for each of the past 30 years. [It also seems unlikely to me that end-of-year news reports on a low clearance rate in a given year would later be updated as cases are subsequently closed. The tracking system, to me, seems logical even if it requires explanations and disclaimers.]

Readers of this blog also know that this happens, those less frequently, with victims who are wounded in a previous year and later die. Earl Brown was shot in 1999 in the 2200 block of Callow Ave., and went on to live for years until suffering a seizure on Oct. 7, 2011. Because the medical examiner said he died from complications of the gunshot wound, Brown, shot 12 years earlier, is a 2011 murder victim instead of revising the numbers from 1999.

Certainly, while the FBI's UCR system smooths over the above mentioned issues, there's no doubt that it also distracts from how many of last year's cases specifically were closed, so let's state the statistics plainly: While DC's 2011 clearance rate falls from 94 to 57 percent when factoring out prior year cases, Baltimore's 46 percent rate tumbles to 33 percent because of 26 cases from prior years that were closed. Thirty-three percent is obviously a figure police officials are not pleased with, though 46 percent isn't being hung from a banner outside of the Bishop L. Robinson Administration Building either.

Several cases from 2011 have been solved so far this year - and added to the 2012 clearance rate.

What do you think? 

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