The problem is not the inclusion of homicides cleared in 2011 that may have occurred before 2011, but the use of a single statistic to represent the effectiveness of the department’s homicide unit. As most applied statisticians know, using a single indicator to measure a complex social construct presents a very limited, and often distorted, view of reality.

To offer a more complete representation, I propose that the police department report three annual statistics instead of one: (1) the true annual rate of homicide clearances — i.e., the number of killings cleared in a given year divided by the number of homicides that occurred in that year; (2) the three-year homicide clearance rate — i.e., the number of homicides cleared in three years divided by the total number of homicides committed over those years; and (3) the average length of time it takes detectives to solve a homicide. These statistics would allow Chief Lanier to take credit for homicides cleared over a multiyear period while still showing the complexities associated with conducting investigations and solving crimes in one of the most challenging big-city environments in the country.

Robert J. Kane, Fairfax

The writer is a senior fellow at the Center for Violence Prevention and Community Safety.

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Why all the fuss over reporting homicide closure rates? The front-page article didn’t question whether the closures were valid; rather it took umbrage with noting closures within a certain time frame. I understand the impurity this causes from a statistical standpoint, but for the public, a closed case is a good thing, regardless of the timing. These aren’t retail figures “same store sales against previous year”; these represent the pursuit of justice. The takeaway: Police will continue to pursue cases and close them out this year, next year, however long it takes.

The real focus and line of questioning should be, “What percentage of the cases closed resulted in conviction?” Does the work to close the case mean the prosecutors are presented with good evidence to use in court? That is what matters most.

Dennis O. Smith, Columbia

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I was a homicide detective in the 1990s when the Metropolitan Police Department transitioned from straightforward crime reporting to the FBI’s Uniform Crime Reporting (UCR) standard. While statistically speaking the UCR numbers are misleading, the approach has its merits. Before UCR, the success of the police department was based only upon current-year case closures, so detectives were given little incentive to pursue prior-year cases.

After UCR, every case counted, freeing detectives to put their focus where needed. For families of past victims, it made an enormous difference. And for the detective, UCR allowed for a truer picture of actual productivity and success.

Gregory R. Sullivan, Great Falls

The writer was a homicide detective and vice patrolman with Washington’s Metropolitan Police Department for 19 years, ending in 2009.