Wednesday, August 22, 2007

Case cleared

A comment late last night on yesterday's blog post Maytag repairman merits a longer response. The comment asked how Lincoln's clearance rate on murder, business robbery, and auto theft compares with other cities. A clearance, by the way, is basically a "solved" case--usually through arrest. These crimes are good choices for comparison, because of all the Part 1 offenses, they are probably the least susceptible to varying reporting practices--it's hard to write off a missing car, a stick-up, and a corpse as anything other than an auto theft, a robbery, and a murder.

The author of the comment hypothesizes that clearances decrease as population increase. This indeed appears to be the case. Although there are a few deviations, the pattern appears to be correlated with size. I must admit, I did not know that, nor suspect it until I looked this morning.

The specific answers, now. I can't break out business robberies from all robberies, but the other data is pretty easy to find on the FBI's Uniform Crime Report site, and in the LPD Annual Reports. The column contains the average clearance rate for Lincoln over the past decade, the 2006 national clearance rate for Group II cities (100,000 to 249,999), and the 2006 clearance rate for all U.S. cities:

Crime Lincoln GroupII All Cities
Murder 95% 55% 61%
Robbery 40% 23% 25%
Auto theft 33% 10% 12%

Of all the Part 1 offenses, the only one for which Lincoln's clearance rate is lower than other cities is rape. Our ten year average was 27%, the Group II average was 39%, and for all cities it was 41%. I have my own theory about that, but I'd rather hear yours first.


Anonymous said...

Not my belief but is it because we are a college town and more reported sexual assaults are false?

Anonymous said...

Thank you for the stats (that was my inquiry last night). My boring layman's hunch on the lower rape case clearance is that a higher percentage of the rapes that occur in Lincoln are actually reported, whereas in the other cities a rape is less likely to be reported. If it's not reported, it's not on the books. This could give the impression that rape is more common in Lincoln than in, say, Chicago, which goes against all common sense. Maybe a pro could parse my gibberish and make sense out of it.

Tom Casady said...

12:44, I think you are right. Comparing our data on rape to other violent crimes across jurisdictions would confirm your observation.

There is a second reason, IMHO. I think many departments overuse "cleared by exceptional means", which is defined, straight out of the UCR Handbook as follows:

Cleared by Exceptional Means—A clearance in which some element beyond law enforcement control prevents filing of formal charges against the offender. Agencies can clear an offense exceptionally if they can answer all of the following in the affirmative. (1) Has the investigation definitely established the identity of the offender? (2) Is there enough information to support an arrest, charge, and turning over to the court for prosecution? (3) Is the exact location of the offender known so that the subject could be taken into custody now? (4) Is there some reason outside law enforcement control that precludes arresting, charging, and prosecuting the offender (for example, suicide, deathbed confession, double murder, etc.)?

We scrupulously follow these guidelines, and have cleared only about 5% of our rapes by exception since 2000. I think this is far below most cities, where exceptional clearances are more liberally applied. I am not implying that they cook the books, but there is a lot of fast-and-loose UCR coding that fails to follow the precise FBI guidelines. We submitted to a voluntary FBI audit at our own initiative to make sure we are doing it right.

Check out this example from the news, or pages 129 and 130 from this report.

Rosey said...

If there is an over reliance on the Exceptional Means clause - wouldn't it be consistent across all crimes and not just rape?

Unless you are suggesting that the stigma for rape is such that it pressures agencies to use that escape route - when they might not use it to boost their burglary numbers?

Tom Casady said...

It's just my theory, but it has been borne out by looking at a few other agencies' data. The FBI does not break down clearance by exception and clearance by arrest, but I found a few individual agencies on the web that do so in their own published reports. We're very low on exceptional clearance in comparison.

The reason it's plausible to me that it's overused more in rape than in other crimes is this: it's not uncommon for a rape victim to decide, at some point, that she doesn't want to go on with the investigative process. My theory is that in many departments, these cases routinely are "cleared by exception," because the victim won't participate,when in fact they don't actually meet the criteria because there is not yet enough evidence to support an arrest and charge. I think this is more likely in rape than in any other crime.

Why would the exceptional clearance rate for rape the State of Utah (page 56) be almost double the rate for other violent crimes, more than seven times the rate for crime overall, and triple that of the City of Lincoln?

Any grad students out there looking for a thesis or dissertation topic?

Ken said...

I came across this site Googling for a definition of "cleared exceptional," which I saw on a police blotter. Your definition is handy, although I'm a little unclear on, in a practical situation, when it would be used.