About: St. Louis County

These notes explain caveats and methodology specific to the St. Louis County section of our Crime Tracker. For general notes about the entire app, go to the main About page.

Fragmentation in St. Louis County

As we developed a crime tracker for St. Louis County, fragmentation created obstacles: there are more than 50 separate police departments in the county.

To get monthly Part I crime totals for all these police departments, plus incident data, we rely on two primary sources: the St. Louis County Police and the Missouri Highway Patrol.

St. Louis County Police provide the Post-Dispatch with incident-level data, but only for:

• unincorporated areas and municipalities that the county patrols
• municipal police departments that contract with the county for crime reporting and analysis

Some police departments, though, either haven't granted the county permission to share incident data, or do not contract with the county for crime reporting. Our crime tracker does not include incident maps for these departments.

We obtain monthly totals grouped by type of crime from the Missouri Highway Patrol for every area police department. County police provide similar totals for each county precinct.

Police departments are required by state statute to report monthly crime data to the Missouri Highway Patrol. Some police departments in St. Louis County are slow to submit data, or in extreme cases, fail to submit data for a given month. Year-over-year comparisons aren't possible if months of data are missing, so we note this circumstance prominently on all applicable report pages.

Jurisdictions

Our map and our crime reports are organized by police department, not by municipal boundaries.

Some police forces patrol just a single city, while others have contracts to patrol neighboring cities, such as St. John police who also patrol Sycamore Hills. Multi-city departments report crime totals as one jurisdiction to the Missouri Highway Patrol, so we treat them the same way in our crime tracker.

The exception is St. Louis County Police, where we break out separate reports for each of its precincts and its MetroLink Unit.

In cases within the past two years where a municipality closes its own department and contracts with a different department for police services, we combine the historical data from both into a single jurisdiction so that we can still make year-over-year comparisons.

In cases within the past two years where a municipality was already contracting with an outside department for police services, then later switches the contract to a different department, we are usually unable to split and re-combine the departments' historical data; this makes year-over-year comparisons misleading, so we note this circumstance prominently on all applicable report pages.

Non-municipal jurisdictions

The following entities are served by their own police forces and report their own crime totals, independent of any cities they may fall within:

• Washington University
• University of Missouri-St. Louis
• St. Louis Community College
• St. Louis Lambert International Airport

Multi-county jurisdictions

• One of St. Louis Community College's campuses is within St. Louis city, but because SLCC is mostly in St. Louis County, the FBI attributes its statistics to St. Louis County.
• A small part of the city of Eureka is within Jefferson County, but because it is mostly in St. Louis County, the FBI attributes its statistics to St. Louis County.
• A portion of the city of Pacific is within St. Louis County, but because it is mostly in Franklin County, the FBI attributes its statistics to Franklin County. For that reason, we have excluded Pacific from the crime tracker.

Incident maps

• As noted in the "Fragmentation in St. Louis County" section above, some police departments either do not share incident data with St. Louis County Police, or have not granted permission to share their data. We display incident maps for the eight St. Louis County Police precincts, as well as many municipal police departments which do share incident data.
• For most incidents, St. Louis County Police provide geographic coordinates where the incident happened, plus a "COGIS" zone code. COGIS zones are a way of dividing St. Louis County into smaller pieces.
• For our incident maps, we use the police-provided coordinates to generate markers on the maps, except in cases of rape.
• Markers for rapes on our incident maps are only approximations. To avoid identifying victims, St. Louis County Police do not provide exact coordinates for incidents of rape. Instead, they provide only the much broader COGIS zone code. On our incident maps, we display an approximate location by calculating the geographic center of the COGIS zone where a rape took place.
• Incidents which lack both coordinates or addresses are excluded from our maps.

Per-capita crime rates

• At this time, we are not calculating per-capita crime rates for St. Louis County. We hope to change that in the future.

Charts

• Each jurisdiction's report page includes a "total crime by month" chart and two "year-over-year change" charts.
• We fix the scale of these charts so that scale is the same on every jurisdiction report page in St. Louis County. Doing this allows readers to compare the charts visually from page to page. This design choice also helps avoid exaggerating small numbers in places with little crime.