About one-quarter of victims of aggravated assault and battery failed to get counted in Chicago Police statistics for 2012, according to a city Office of the Inspector General report.

The audit reviewed a sample of 383 assault-related incident reports out of a total of 83,480 for 2012, said the Chicago Sun-Times.

Police officials explained that the Illinois Uniform Crime Report, which is created annually by the Illinois State Police, changed the way aggravated assaults and batteries were reported in 2011. The Uniform Crime Report went from counting “incidents” to counting victims. Multiple victims can be part of each incident.

The Chicago Police Department, which was headed by police Supt. Jody Weis in 2011, failed to change the way those crimes were reported. The problem came to the attention of police Supt. Garry McCarthy in late 2013, said CBS Local.

"McCarthy ordered a review of 2012 and 2013 reports of aggravated battery and assault. He also is changing the field manual for officers, so they know how to report those crimes accurately," said CBS Local.

The audit didn’t address the way the Chicago Police Department counts shooting incidents. Shootings are not included as a category in the Illinois Uniform Crime Report, but the statistics are used internally by the Chicago Police Department. The shooting statistics count each incident, but not each victim.

The audit also didn’t examine the classification and reporting of murders. Of the 6,260 homicides reported on the city’s data portal between 2001 and June 12, 2013, all but 19 of them were classified as first-degree murder. Nineteen were counted as involuntary manslaughter or reckless homicide, said CBS Local.

“We concluded that the present risk of downgrade [from first-degree murder to a lesser offense] was low and therefore did not audit this category,” the inspector general’s report said.

The report found that Chicago Police officers “incorrectly classified 3.1 percent of 2012 assault-related events contained in incident reports.” For example, the victim and offender were former roommates in one case. Due to their relationship, the correct code for the incident was “domestic simple battery,” but the officer coded the incident as a “simple battery.”

The 3.1 percent error rate was under the 10 percent error rate that the FBI states is acceptable for agencies participating in its national reporting program, according to the inspector general, said CBS Local.

“Data analysis is central to CPD’s pursuit of its critical public safety mission,” Inspector General Joe Ferguson said in a prepared statement. “The integrity and reliability of crime statistics used for those purposes hinges on two features — the accuracy of incident reporting from the field and the accuracy of the classification and reporting of that information once entered into the system.”

“CPD’s robust response to the problems the audit revealed is an encouraging sign of an organization seeking to improve. We caution, however, that what is reported out is only as reliable as what is fed into the system from the field. Public confidence in crime statistics therefore also depends on the accuracy of field reporting, which we did not test.”

Read more: http://chicago.cbslocal.com/2014/04/07/chicago-police-underreported-number-of-2012-assaults-audit-finds/