The data is retrieved from CLEARMap, the crime mapping Web site of the Chicago Police Department (CPD).

The data is updated daily, but the police department introduces a week delay between when a crime takes place and when the data is made available. This means there's at least a week delay between when a crime is reported and when that report appears on EveryBlock.

To report crime in Chicago, dial 911.

This data reflects incidents where the police responded and completed case reports. Note that a case report is not necessarily issued every time the police respond to an incident. Note also that though many case reports are the result of calls to 911, this data is not a list of 911 calls.

A report's "crime type" classification is based upon information known at the time the preliminary investigation was conducted. It could be revised at a later time. For example, "Assault" could be changed to "Aggravated Assault," or vice versa. When a crime type is revised in the source data, that is reflected here at EveryBlock, but there is no indication that the crime type was changed from its original value.

Crime classification codes are derived from the Uniform Crime Reporting (UCR) Program of the Federal Bureau of Investigation's (FBI) National Incident-Based Reporting System (NIBRS). See the UCR Handbook (PDF) for a complete listing and explanation of crime types.

The crime classifications have been summarized due to the often lengthy and complex nature of the crimes. These definitions are not verbatim, may not include every element of every offense, and should not be used in a court of law or for legal reference. They are only basic attempts to describe primary classifications. See the Illinois Compiled Statutes for thorough and accurate definitions of the law or interpretations of the law. See also the City of Chicago Municipal Code (MCC).

See the Checkerboard Chat weblog ("Of the Police... By the Police... For the Police") for daily posts about the police department, including commendation letters to the Superintendent and specific details on the exploits of officers.