Convicted in Cook

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This project is an analysis of five years of Cook County conviction data. The information was received by Tracy Siska of the Chicago Justice Project from the Office of the Chief Judge of the Circuit Court of Cook County through a request to the chief judge. We've posted a copy of that request here.

Each year, tens of thousands of people stand in front of judges at the Cook County Circuit Court, the largest unified court system in the country. Their offenses range from marijuana possession charges that result in low-level misdemeanor convictions to multiple murders that put people behind bars for life.

When a violent crime is picked up by the news media, it's often sensationalised so that every minor detail is brought into the public purview. Meanwhile, the vast majority of convictions - mostly drug related - are given little notice.

This project will attempt to answer several questions regarding convictions in Cook County. Upon first receiving the data, it became apparent that the data was messy and incomplete.

While we would have liked to have seen all convictions from 2005-2009, we aren't sure if we received them all because we have only limited information on the total number of cases in the court system with which to compare the data. Our data didn't include the initial charge or if an individual had prior convictions that impacted the court's ruling on their case. Our original request asked for the data to include race, though it was not provided. While the Chicago Justice Project's request only asked for information on adults, several entries found in the data included minors.

The team at FreeGeek Chicago helped us clean the data, visualize it, and answer the questions we posed when we first obtained the data.

What we wanted to find

  1. Many maps of negative social effects show concentrations on Chicago's South and West Sides. Is there a similar pattern with convictions?
  2. Of all convictions in Cook County, what are the top ten offenses?
  3. Of all felony cases filed, how many result in a conviction?
  4. For drug convictions, what are the most common types and class of convictions?
  5. How do convictions vary by age?
  6. From research, we know that violence against women occurs across all socioeconomic and racial groups. Does the conviction data follow a similar pattern?
  7. How are DUI (Driving Under the Influence) convictions spread throughout the city?

Here's your city

We've mapped how convictions are spread around the city and suburbs in Cook County. For the city, we have divided the map into individual community areas. For suburban areas, the map groups areas by their municipality.

Community areas in the City of Chicago with the highest conviction rates, have more convictions per capita than any suburb of Cook County. However, there are some suburbs with relatively high rates of per capita convictions.

The data shows higher amounts of convictions in areas with fewer economic resources. The convictions data alone doesn't provide an explanation for this trend. However, other studies have consistently shown this correlation.

Click on a community area or suburb to see the number of convictions in an area, and convictions per capita.

Cook County's top ten

Position Statute Charge Description Count Percent
1 720-570/402(c) Possession of Controlled Substance 31,183 20%
2 720-5/16a-3(a) Retail Theft 10,430 7%
3 625-5/11-501(a) Aggrevated DUI 8,689 5%
4 720-570/401(d)(i) Manufacture or Delivery of Controlled Substance, Other Amount Narcotic/Schedule I & II 8,361 5%
5 720-5/19-1(a) Burglary 7,485 5%
6 720-5/24-1.6(a)(1) Aggregated Unlawful Use of a Weapon 5,473 3%
7 720-570/407(b)(2) Manufacture or Delivery of Narcotics/Schedule I & II near school, public housing, etc. 4,326 3%
8 720-5/24-1.1(a) Unlawful Use or Possession of Weapon by Felon 4,160 3%
9 720-5/16-1(a)(1) Theft 3,753 2%
10 720-570/401(c)(2) Manufacture or Delivery of Cocaine (1 g or more but less than 15 g) 3,612 2%

There are several possible explanations for the majority of convictions being for low-level drug crimes. We know nationally that at least 90 percent of all convictions are the result of a plea deal. We have no reason to believe the Cook County rate meaningfully varies from this national rate. Also, it is common for crimes such as "possession [of a drug] with intent to sell" to be reduced as a result of a plea deal. These crimes are commonly reduced to felony possession if a case cannot be made in court for an individual to be tried on the original charge.

As the map below shows, the most common convicted offense throughout the city is possession of controlled substance. Driving under the influence (DUI) is another common offense, with community areas where this was the most common convicted offense forming two distinct belts. We chose not to map the most common convicition in suburban places because the number of convictions for the most common offense was often so low, or differed by so little from other types of offenses, that the map would give a distorted view of suburban offense trends.

Low level felonies most filed, and convicted

A separate data set, from the Circuit Court of Cook County, shows that 173,204 felony cases were filed between 2005 and 2009. The majority of these were the lowest-level felonies - class 4.

The data requested by the Chicago Justice Project shows that, during the same time period, 145,487 cases that were filed as felonies resulted in a conviction, with 144,835 of those cases resulting in a felony conviction. This number is smaller than the number of cases filed not only because some cases did not result in a conviction but because the data reflecting cases that resulted in a conviction may not contain records for cases that were filed in 2005-2009 but had not been completed when the data was requested.

In addition, plea bargain cases in Cook County Court have a significant effect on the final convictions. Some of the cases in the data were filed with charges for high-level felonies and later amended to lower-level felonies or misdemeanors.

Drug crimes make up the bulk of convictions

By far the largest category of convictions are drug convictions. When an individual is arrested on a drug charge, they can be booked for manufacturing and delivery, or for possession. Whether it is one or the other depends on many factors - the patrolling officer, whether a person has any priors, or even whether they're able to make a deal with the prosecutor.

The majority of drug-related convictions in Cook County are for possession.

Convictions can vary by amounts, but what really matters is the class of a felony or misdemeanor. Many things can impact the class of a conviction - from how the product is packaged to what an individual said during an arrest.

In this graphic, we divided drug charges by their class. The majority of possession charges were class 4 felonies, meaning the majority of people were convicted for the lowest level felony.

Youth carry overwhelming number of convictions in Cook County

Street crime skews young.

It isn't entirely clear why this is the case, but criminologists theorize that most people simply age out of crime. Following the Bureau of Labor Statistics cut-off age for youth - 24 - most people commit less crime and often stop altogether by 35. An individual's desire to have a family and whether they have access to legitimate employment impacts the likelihood they will commit a crime. The national youth unemployment rate in July of 2014 was 14.3 percent. For African-American youth, unemployment spikes to 23.8 percent. The areas that have the most convictions also have high populations of African-American under the age of 24. As a reminder, the data does not indicate the race of the convicted individual.

What the data does indicate is that from 2005 to 2009, Cook County convicted nearly twice as many young people between the ages of 18 and 24 as the next most convicted age group.

Total convictions by age

Young people also account for the largest numbers of convictions for certain categories of offenses. Our data shows that the vast majority of convictions for violent index offenses are of young people.

Violent convictions by age

Drug convictions by age

A slice of reality: convictions for sexual and domestic violence

When we started the project, we wanted to gain more insight into those convicted of sexual and domestic violence. However, less than 2 percent of all convictions in Cook County from 2005-2009 were for sexual assault and domestic violence. We defined this category to include crimes such as domestic battery, stalking or violating an order of protection.

Though the data does not indicate any details about the people victimized by these crimes, we know they are heavily underreported. The National Crime Victimization Survey estimates that only 28 percent of sexual assaults and 55 percent of domestic violence is reported. One of the few things we were able to discern from the data is that far more convictions for these types of crimes are of men than women.

We also know from other research that the vast majority of offenders have a relationship with the survivor to some degree. While stranger attacks may receive the majority of reporting in local news, they are a statistically small part of sexual and domestic violence. Because our data does not address victimization, it is difficult to place a figure on who is affected by these crimes, and their relationship to the accused.

The number of domestic and sexual violence convictions were too low (2,309 convictions out of 159,235) to perform any reliable analysis. When we attempted to examine these convictions geographically, we did not observe any significant trends. Further research will be required to answer questions around domestic violence convictions.

For every conviction of a woman for this category of crime, there were 31 convictions of men. There were a total of 2234 convictions of men and 73 convictions of women.

DUI convictions are spread across the city

Driving under the influence (DUI) is one of the most frequent offenses for convictions. The top twenty Chicago neighborhoods for DUI conviction rates are spread across the city. Interestingly, neighborhoods with widely disparate overall conviction rates, such as West Garfield Park and Irving Park, have similar conviction rates for DUI. In this case, Irving Park, which has a slightly lower DUI conviction rate, has more than twice the number of DUI convictions as West Garfield Park.

Here's the top 20 community areas for DUI convictions in order of convictions per capita. Note that the conviction rate has been rounded:

Position Community Area DUI Convictions per 1000 residents DUI Convictions
3 NEW CITY 6 273
5 HERMOSA 6 139
9 GAGE PARK 4 159
11 ALBANY PARK 4 193
13 AVONDALE 4 148
14 IRVING PARK 4 195
18 ROGERS PARK 3 171
20 AUSTIN 3 297

About the data

Data analysis

One of the key challenges in analyzing our data was understanding the records in our spreadsheet and learning how they related to other important but unrepresented parts of the criminal justice system.

Below, we've listed the difficulties we encountered, and how we dealt with them.

We don't know if we received every conviction.

We requested all available data for cases that resulted in a conviction from 2005-2009. What we received was a mixture of data. Some of our data was from cases that resulted in a conviction during our time period. We also received disposition records for cases that resulted in a conviction prior to our time period. We believe many of these dispositions resulted from probation violations but we don’t have enough data to confirm this in every case. To make sure we were analyzing all of the dispositions in a case, we excluded cases that were opened before 2005 from our analysis.

Because even aggregate counts of cases and convictions in Cook County are not available for public access, we are unable to determine if we received data related to every conviction as we requested. The Clerk of the Circuit Court of Cook County, the office that maintains the Court’s data, did not provide us aggregate totals of convictions & dispositions that would allow us to confirm the contents of the data.

We don't know how many cases were dismissed or resulted in an acquittal.

Since the data only contains records for cases that resulted in convictions, we don't have any records for cases that were dismissed or resulted in an acquittal. More broadly, we don’t know the total number of cases filed.

We don't know an individual's initial charge.

The data reflects what happens with a criminal case once it proceeds through the court system, so we don’t know the initial charges of the individuals who appear in our data. While we were given some information about the individuals in the dataset, such as home address, the data didn’t include their race, or their prior convictions.

A record in the dataset isn't necessarily a conviction.

Each row in the dataset represents a disposition in a criminal case that resulted in a conviction. Dispositions are judicial actions in a case. They represent convictions, but also changes in a charge, a case being postponed or a case switching to a different judge. We had to extract convictions from these records.

The vast majority of cases are concluded behind closed doors, from the negotiations leading to a suspect's charge through to, most often, a resulting plea deal. The experience of most people who come through Cook County's courts is far removed from the portrayal of jury trials on television.

Crime values were not entered consistently.

The data was analyzed primarily by the type of crime that resulted in a conviction and where the convicted person was from. The type of crime is identified in the data by statute and charge description fields. However, these values were not entered consistently. We examined the data and used a variety of database queries to try to group records that corresponded to the same type of crime.

There were frequent misspellings and inconsistent abbreviations.

Similarly, there were frequent misspellings and abbreviations for city and state values for the home address. In other cases, an individual's home address may be a correctional institution or they may be homeless. Where we could, we used the street address and zip code to geocode the home address and map them to a Chicago community area or suburb.

Data processing

In order to analyze the data and make it available for public access, the project team had to load the raw data, which was provided in comma-separated values (CSV) format, into a database. We also had to perform multiple transforms on the data in order to make it easier to query the data for our analysis. The data loading and transformations are performed by a series of Python scripts. You can view the source code repository for the scripts here. You can read an in-depth description of the data processing steps here.

The story behind the story

This data is public information, but it didn't come easily. It took the Chicago Justice Project over two years to obtain the data used in this project.

What we asked for: all the data involved in all the cases that entered the court for a five-year period, whether or not the case ended in a conviction, and identifying categories such as race.

Explore the data

Explore the data

Explore the data

Request your own data

The current process to gain access to Cook County Circuit Court data requires a three-step process.

  1. File a request through snail mail with the Office of the Chief Judge of Circuit Court of Cook County, Judge Timothy Evans. This request should detail the data you are seeking to access.

    Send requests to:

    Office of the Chief Judge
    Circuit Court of Cook County
    50 West Washington Street, Room 2600
    Richard J. Daley Center
    Chicago, IL 60602
  2. Upon the Chief Judge's approval of your request it is sent the Clerk of the Circuit Court to be fulfilled. The Clerk's Office maintains the data for the Courts.

  3. Often the Clerk's office will require a fee both for programming time and for computer time to extract the data from their systems to fulfill your request.

How can we make the data more open?

  • no fees
  • full data available
  • searchable, electronic court records