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U.S. Department of Justice Nation311nstltute of Justice

103445

This document has been reproduced exactly as received from the person or organization originating It. Points of view oropinions stated in this document are those of the authors and do not necessarily

represent the officiai position or policies of the National Institute of Justice.

Permission to reproduce this copyrighted materiai has baen granted by

Illinois criminal Justice Infor.mation AUthiOlty

to the National Criminal Justice Reference Service (NCJRS).

Further reproduction outside of the NCJRS system requires permission of the copyright owner.

Specification of Patterns over Time In Chicago Homicide:

Increases and Decreases, 1965-1981

October 1985

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by Carolyn Rebecca Block

\ ...,". .,,,' .

Statistical Analysis Center

NC~iU!l \

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illinois Criminal Justice Information Authority

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William Gould, Chairman

J. David Coldren, Executive Director

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I Table 'of Contents

I Executive Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. iii

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Acknowledgements . . . . . . . . . . . . . , . . . . . . . . . . . . . . . 0 ? , ? 0 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ix

Introduction . . . . . . . . . . . . . . . . . . . . . . . ". . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

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Homicide from Two Perspectives: Aggregate and Time Series ....................... 2 Summary of Analysis from the Aggregate Perspective ........................... 3

Profiles of White. Black. and Latin Homicide . .??..........?............... 3

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Typical Ages . .........................?.........?................ 4 Gender . ......................................................... 5 Weapon Use . ..................................... , .............. 5

Multiple-Offender and Gang-Related Homicide . ?.........??............... 6

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Interracial Homicide .........................?.....?............... 6 Demographic Explanations of Homicide Patterns over Time. '.' .................... 7

Time Series Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

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Outline of Paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 8 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Methods . . . . . . . . . . . . . 11 c ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ? 0 ? ? ? ? ? ? ? ? ? ? , ? ? ? ? ? ? ? ? ? ? ?

Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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Police Investigation Data . . . . . . . . . . . . . . . ? . ? . . . . . . ? . . ? . . . . . . . . . . . . . . . 12

Population Data: Rates vs. Raw Numbers . . . . . . . . . . . ? . . . . . ? . . . . . . . . . . . . . . 12

Counting Offenders in Multiple-Offender Homicides . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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Murder Attributions . . . . . . . . . . . . . . . . . . . . . . . . . . ? . . ? . . . . . ? . . . . . ? . . . . . 13 Analysis of Race and Gender . . . . . . . . . . . . . . . . . . . . . . . . . ? . . . . . . . . . . . . . . . 15

Other Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15

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Race/Ethnicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ? . ? . . ? . . . . . . . . . 15 Precipitating Crime . . . . . . . . . . . . . . . ? . . . . . . . . . . . . . ? . . . . . . . . . . . . . . . . . 16 Teen/Youth Gang .... : . . . . . . . . . . . . . . . . . . ? . ? . . . . . ? . . . . ? . . . . . . . . . . . 16

W e a p o n . 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ? ? ? ? ? ? ? .. ...

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Unsolved Cases and Robbery Homicide ..................................... 17 Times Series Pattern Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Criteria for Time Series Specification ...................................... 19

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Seasonal Analysis .................................................... 20 Circumstance, Weapon, and Number of Offenders . . . . . . . . . . . . . . ? . . . . . . . . . . . . . . . . . 21

Precipitating Crime ...................... , ............................... 22

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Weapon ................................ , . , , .. , .. , .. , ... 0 ?? , ???? , ?? 24 Multiple-Offender vs. Single-Offender Homicides ............................. 26

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Population Patterns ..................................................... 29

Race/Ethnicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Victimization of Whites, Blacks, and Latins over Time . . . . . . . . . . . . . . . . . . . . . . . . . . 33

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Robbery Homicide Victimization, by Race/Ethnicity and Weapon . . . . . ? . . . . . . . . . . . . 35 Interracial Homicide ..........................?....................... 36

Robbery Homicide . ?.................?............?...???......... 36

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37 Assault Homicide . . . . . . . . , . . . . . . . . . 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? , ?? Intraracial Assault Homicide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

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Illinois Criminal Justice Information Authority

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Weapon and Intraracial Assault Homicide ................................... 4 1

Race/Ethnicity and Precipitating Crime: Multiple Offenders . . . . . . . . . . . . . . . . . . . . . . 42

Robbery Homicide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Assault Homicide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

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Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . t. ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 44

Gender ................................... ".......................... 47

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Victimization of Males and Females over Time ............................... 47

Victim's Gender and Precipitating Crime ............?...................... 47

Offender's Gender and Precipitating Crime ??.?....?......................... 49

R o b b e r y Hotnicide 49 0 ? ? 0 ? 0 ? ? ? ? ? ? ? ? ? ? ? ? ? , ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 0 ? ? ?

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Assault

H o m i c i d e . . . 4 9 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Intergender and Intragender Assault Homicide . .......................?... 49 Offender's Gender and Race/Ethnicity in Assault Homicide . . . . . . . . . . . . . . . . . . . 50

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Gender. Race/Ethnicity. and Weapon in Assault Homicide . . . . . . . . . . . . . . . . . . . . 52

Domestic Homicide and Race/Ethnicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , ......... , . . . . . . 54

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Age ................................................................ 55

Age of Victim over Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Weapon and Age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

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Age, Race/Ethnicity, and Gender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Weapon, Precipitating Crime. and Victim's Age . . . . . . . . . . . . . . . . . . ? . . . . . . . . . 60 Interage Homicide . . . . . . . . . . . . . . . . . 63 \I ? ? ? ? ? " ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

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Age of Offender over Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ? . . . . . . . . . . . . 63

Age and Precipitating Crime: Assault and Robbery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Race/Ethnicity and Offender'S Age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , .... 68

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

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Summary and Discussion .................................................. 75 Summary of Homicide Patterns over Time .................................. 75

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Types of Homicide that Were Stable . .................................. 75

Patterns in the Late 196 Os . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 The 1974 ,Peak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Patterns from 1977 through 1981 .................................... 77

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The Demographic Hypothesis .......?........?.......................... 79

Unexpected and Unexplained Findings .?................... ; ............... 80 From Description to Explanation ......................................... 8 I

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Appendices ........................................................... 85 I: Chicago in State and National Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

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II: Gender and Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , .... , ... , . , .. ,92

III: Yearly Frequencies: Some Less Common Precipitating Crime . . . . . . . . . . . . . . '" ... 94

Notes ............................................................... 95

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References ........................................................... 97

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Illinois Criminal Justice Information Authority

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I Executive Summary

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Chicago police recorded 12,872 homicides from 1965 through 1981. This paper is the second

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of two reports that examine these homicides. The first report, Lethal Violence in Chicago over Seventeen Years, describes the overall characteristics of homicide in Chicago, and answers questions

such as these: Who are the victims of Chicago homicide?; Who are the offenders?; Are certain

racial/ethnic, gender, or 'age groups in Chicago's population overrepresented among homicide vic-

tims or offenders?; Does one racial/ethnic, gender, or age group tend to prey on another--for ex-

ample, interracial attack, domestic murder, or murder of the elderly by teenagers?; Are some

homicide situations--such as robbery homiciue, teen gang homicide, firearm homicide,

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male/female homicide, multiple-offender homicide--more common among certain population groups?

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This second report focuses on the pattern over time in the number of homicides occurring from month to month. The number of homicides known to the police in Chicago changed tremendously over the 17 -year period (see figure 1 on page I). In I 965, there were about 30

murders in a typical month, but by the end of 1974, there were almost 75 per month. After a

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brief decline in 1975 and 1976, homicides increased again from 1977 through 1981. Was this pattern over time evident in murders involving only one part of Chicago's population, or did it

occur without regard to race/ethnicity, gender, and age? Did it occur in only one type of homicide

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or in all types? Together, the two repo'rts describe Chicago homicide from two perspectives--the relationship

among victim, offender, and situation in all 12,872 homicides; and the change over time in these

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homicides. Relationships that are important in the aggregate of all homicides are not necessarily important in determining patterns of change in the number of homicides occurring from year to

year. Only by looking at homicide from both perspectives--the 17-year aggregate and the change

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over time--can we derive an accurate description of Chicago homicide. Unless we have an accurate description, any attempt at explanation would be at best fruitless and at worst erroneous.

The first report demonstrates that homicide is not one crime, but many. Typical victim and

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offender characteristics differ for homicides that begin as a fight, brawl, or argument (assault homicide), for robbery homicide, for burglary homicide, and for rape homicide. In each of these

homicide types, crimes committed with and without firearms have different characteristics, as do

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single- and multiple-offender homicides. In addition, certain homicide subtypes, such as arson homicide and teen/youth gang homicide, have their own characteristics. As a result, answering a

seemingly simple question, such as one concerning the involvement of certain racial/ethnic, gender,

or age groups in homicide, requires a complex answer.

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This complexity occurs not only in a description of aggregate homicide characteristics, but also

in a description of homicide changes over time. Because different types of homicide have different

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characteristics, each type responds differently to changes in society, such as increases or decreases in unemployment, population density, or firearm availability. As a result, different homicide

types follow different patterns of change over time. Therefore, an explanation of the rapid in-

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creases and decreases that occurred in the total number of homicides in Chicago from 1965 through 1981 must be built on a foundation of detailed descriptions of patterns of change over time in each homicide type. If certain types of homicide did not change at all during this volatile

period, then those types cannot explain the increases and decreases in homicide as a whole. If we

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want to explain the rapid increase in Chicago homicide from 1965 to 1974 and ,the increase from 1977 through 1981, we should focus on those types of homicide that changed, not the types that

remained stable.

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