look at rates of clearance by the police of various categories of robbery. A second section addresses some implications of this study for criminological theory and criminal law. The study collected data on robbery experience in the city of Chicago over a twelve-month period. Our central interest is those factors and conditions in robbery events that cause victim injury and death. Chicago is a large city with a large volume of robbery, robbery resulting in victim injury, and robbery killing. 5 The study period extended from October 1, 1982 , through September 30, 1983 . For that period we gathered data on all killings classified by the police as robbery related (a total of ninety-five), on the 142 killings for which no motive was assigned by the police, on a sample of 346 robberies resulting in victim injury, 6 and on a sample of 360 nonlethal robberies of all kinds that were reported to and recorded by the Chicago police. 7 The data in this study were collected prospectively-or, more accurately, almost prospectively-rather than as a historical record of past events. Each month, the fatalities and sample of nonfatal cases were referred to us within a short period after the police report. In many of the death cases, we were thus able to interview police while an investigation was still in progress or shortly after it concluded. We were often able to correct misstatements or premature inferences in the paper record of the case and to benefit from the developing insights of the investigation process. I. THE STUDY Our analysis compares three different types of robbery events: those that result in death, those that cause injury, and a representative sample of all nonfatal robberies reported to the police. The first section of this paper reports on our efforts to estimate the frequency of robbery killings using homicide records of the Chicago police. The next section compares the profile of fatal robberies with a sample of nonfatal robberies obtained from offense reports submitted to the Detective Division of the Chicago Police Department. Finally, we introduce a special sample of offense reports indicative of serious injury that are contrasted with robbery killings and representative nonfatal robbery events. A. Estimating the Volume of Robbery Killing A first approximation of Chicago's robbery killing rate can be derived from police statistics. In 1983, Chicago police reported that a total of 115 criminal homicides were classified as robbery related-16 percent of that year's homicides, and a rate of 3.8 per 100,000 population. When robbery killings are compared with the volume of officially reported robberies (23,471 in 1983) , the police numbers produce an official death rate of 4.9 per thousand robberies. 8 There is reason to believe that estimates of robbery killing based on such aggregate statistics are inaccurate. One problem, largely beyond the scope of this study, is that only a proportion of all robberies occurring in Chicago are reported to the police by victims. A second problem is that many of the robberies reported to the police by victims are not so classified by the police in official statistics. A. Estimating the Volume of Robbery Killing Underreporting, both to and by the police, reduces the number of robberies in the denominator of statistics used to derive an official death rate and thus results in a higher death risk estimate for individual robbery events than actually occurs. 9 Underestimating the universe of robbery events, however, does not undermine estimates of the number of robbery killings or the proportion of criminal homicides attributable to robbery. A. Estimating the Volume of Robbery Killing The notion of an overall statistic expressing a death risk for robbery is also misleading because different types of robbery carry different risks of victim fatality.' Aggregating all types of robbery killing and dividing this figure into a parallel conglomeration of diverse robberies produces a total death risk statistic only useful for gross comparisons, even if official statistics on robbery killings were accurate. A. Estimating the Volume of Robbery Killing Unfortunately, official estimates of robbery killings are far from perfect, and the margin of error associated with these statistics is a central concern of this study. Violent killings stemming from robbery do not result in the kind of underreporting to and by the police associated with nonfatal robbery events. Fatal stabbings and shootings inevitably come to the attention of the police and almost always are reported as criminal homicides. Frequently, however, the events leading to a violent killing are not clear to the investigating officers, so that the motive for a violent death cannot be confidently determined. To the extent that robbery killings are not classified accurately by motive, the risk of a robbery event leading to death will be understated by official statistics and the volume of robbery killings will be undercounted. A. Estimating the Volume of Robbery Killing The problem of undercounting robbery killings because of difficulty in establishing homicide motives has become particularly acute over the past two decades as robbery homicide and the number and proportion of all homicides of undetermined motive have increased. In 1965, for example, only thirty-one of Chicago's 395 homicides were classified as robbery related by the police. An additional nine killings, fewer than 3 percent of the total, were classified as motive undetermined."' By the 1970s, however, both official robbery killings and the number of killings of undetermined motives increased substantially. 12 Between 1965 and 1983 the number of robbery killings in Chicago increased more than threefold from thirty-one to 115. The number of killings classified as motive undetermined increased thirteenfold from nine in 1965 to 117 in 1983. When the number of unclassified killings is roughly equal to the total volume of officially reported robbery homicides, the margin of error in estimating the volume of robbery deaths is unacceptably high. A. Estimating the Volume of Robbery Killing One approach would allocate killings with unknown motives among various motive categories in the same proportion as killings for which motive has been determined. For example, there were 612 homicides in 1982 in which the police were confident of the motive of killing. Since 19 percent of these cases were classified as robbery deaths, this method would allocate 19 percent of the motive-undetermined killings (.19 x 117 = 22) to the robbery category, thereby increasing the number of estimated 1983 robbery homicides from 115 to 137. A. Estimating the Volume of Robbery Killing If we knew nothing of patterns of homicide, this "naive" accounting scheme might be an acceptable method of dealing with the uncertainties generated by unclassified cases. However, since it is known that the bulk of all cases of homicide in Chicago involve a prior relationship between victim and offender, ' 3 it is unwise to suppose that an equal proportion of different types of homicide end up in the motive-undetermined category. Domestic and romantic homicides, for example, are about as frequent as classified robbery killings in Chicago homicide statistics. 1 4 The close relationship between victim and offender and the usually obvious motive make it unlikely that many domestic cases will come to the attention of the authorities without providing a sufficient factual basis for a police classification of motive. A. Estimating the Volume of Robbery Killing Robbery killings and unknown-motive killings, by contrast, share a number of characteristics that make police fact-finding difficult and motives hard to classify. A substantial percentage of both kinds of killing involves a victim and offender with no known prior acquaintance, many killings lack third party witnesses, and the motive for the violence must frequently be inferred from sparse circumstantial details. A. Estimating the Volume of Robbery Killing 5 It seems likely therefore that a larger proportion of actual robbery killings arise from cases where the motive is undetermined than any naive projection would estimate. A. Estimating the Volume of Robbery Killing In order to gain a more sensitive estimate of how many motiveundetermined killings are likely to have resulted from robbery motive, we resorted to a reanalysis of the investigative records of reported robbery killings and of those for which motive was undetermined.' 6 All officially (1965 -1973 ), 66 J. Crim. L. and Criminology 496 (1976 Richard Block, Violent Crime 40 (1977) ; Chicago Police Dep't, Murder Analysis (1965-82) . A. Estimating the Volume of Robbery Killing 14 One hundred and four of the 668 murders (15 percent) in Chicago in 1982 were classified by police as involving domestic or romantic relationships. Chicago Police Dep't, Murder Analysis 1982, at 15. This total excludes some triangle killings where the victim is killed by a rival. A. Estimating the Volume of Robbery Killing is In 57 percent of the unknown-motive killings the victim and offender were known to have been strangers or the absence of information created the possibility that they were not acquainted. In about 40 percent of the unknown-motive killings the police were not able to identify any witnesses who were nearby when the incident occurred. In almost half the unknown-motive cases it was not possible for the police to tell with certainty whether or not any of the victim's valuables were taken. Three months after the close of the data collection period (October 1982 -September 1983 , less than a quarter of the unknown-motive killings had been cleared. A. Estimating the Volume of Robbery Killing 16 Cases were reanalyzed by Detective Ed Carter of the Chicago Police Department's Crime Analysis Unit. Detective Carter was asked to perform the reanalysis because of his extensive experience in robbery investigations and his lack of involvement in the original classification of homicide cases. His generous assistance is gratefully acknowledged. Detective Carter reanalyzed 146 cases (ninety-nine cases originally classified as motive undetermined and forty-seven as robbery homicide). The robbery homicide cases were included classified motive-undetermined cases and a large sample of classified robbery killings that occurred during our study period were submitted to a Chicago police detective for his assessment of the probability that the killing resulted from a robbery. The label attached to the official police investigation was not provided to our informant, but the file was not purged of descriptive materials that might alert the rating officer to the suspicions of the investigating field personnel. The result of this exercise is reported in Figure 1 . '7 The first lesson of Figure 1 is that the police are apparently conservative in describing killings as robbery related. The overwhelming majority of killings described as robbery related in the initial investigation were so classified by independent rerating. Because the rerating was based on a paper record generated by initial investigators, the process was probably biased by the views of the investigative detectives as reflected in the file. But the contrast between the rerating of killings that were classified as robberies and those that were classified motive undetermined still supports an inference of conservative robbery classification. A. Estimating the Volume of Robbery Killing Figure I also shows that a sizable proportion of killings classified by police as motive undetermined may have involved robbery. Fifteen percent of the 143 motive undetermined deaths were rerated as probable or very possible robbery killings, and an additional 26 percent were listed as possible robbery outcomes. Thus, in almost four out of ten motiveundetermined killings, robbery offered a plausible explanation for the events as police understand them. both to help mask from Detective Carter the original classification of the cases and to provide a check on the way these cases were originally classified. The reanalysis took place in the following way. For each case the detective was given a file containing the reports on which the original classification was based but devoid of any explicit indication what the original classification was. The detective was asked for each case to respond to the two following questions using the categories given: (1) What is the likelihood that a robbery or attempted robbery was involved in the homicide incident? (a) Probable. Substantial indications of a robbery are present, and they outweigh any contraindications. (2) If a robbery or attempt is likely to have taken place (that is, if the incident was rated a-c above), choose the possibility below that best describes the relationship of the robbery or attempt to the killing. (a) Robbery was the primary motive for the incident leading to the death. (b) Robbery was a consequence of but not the primary motive for the incident leading to death. (c) Not enough is known about the incident to make a reasonable choice. A. Estimating the Volume of Robbery Killing 17 The percentages reported in this figure represent the proportion of victims, rather than incidents, which was assigned to each probability level. In a few robberies more than one victim was killed. To make fatal and nonfatal robberies comparable, subsequent analyses use a single robbery event as a unit of analysis, rather than each death. The tendency to find more robberies in rerating may also be enhanced by the rerating officer's knowledge that the research process he was assisting was a study of robbery. The context of the study creates an atmosphere for decision that is perhaps more conscious of the possibility of robbery involvement than the ordinary police task of classifying homicides by selecting from a number of motive rubrics. Further, this "robbery consciousness" might have been enhanced by the fact that the rerating officer specializes in robbery investigation. INITIAL RATING Killings The consequences for the death rate statistic of adding in rerated cases are estimated in Table 1 . Killings The number of criminal homicides associated with robbery ranges from under 100 (if only the highest robbery-probability category is counted) to 159 (including all possible robbery cases). The corresponding estimate of death risk, in each case based on officially classified robberies, ranges from less than five per thousand to almost seven per thousand. We think that dealing explicitly with the uncertainty of this range of estimates is more appropriate than attempting to put a finer point on matters by selecting an arbitrary cutoff point in the rerating process or using any other single estimation technique. B. Patterns of Robbery Killing One consequence of using a range of plausible estimates is the need to use alternative formulations when discussing patterns of robbery killing or estimating risks associated with different types of robbery events. At Table 2 provides an introduction to the complex nature of robbery killing patterns, comparing officially classified robbery killings during the study period with a sample of 360 nonfatal robberies reported to and by the Chicago police during the same twelve months. The contrast between robberies and robbery killings is striking. Just over half the officially reported robberies occur in street locations, and an additional 10 percent take place in commercial premises. This finding is consistent with the usual public perception of robbery locations. Only one in twelve of the sample of robbery events occurs in a place of residence. Robbery killings are another matter: just under 20 percent occur on the street, and the total volume of killings taking place in street and commercial locations (35 percent) is about equal to the 36 percent of all officially reported robbery killings reported in residential settings. A similar pattern emerges when the relationship between victim and offender is compared in robbery killings and robberies, the task of Table 3 . A majority of robbery killings and of nonlethal robberies conform to the popular perception of robbery as a stranger crime. But more than one out of five robbery killings involve a prior relationship. In addition, no confident judgment could be made about victim-offender relationship in another 24 percent of the robbery killing cases. Thus the police are confident that victim and offender are strangers in just under nine out of ten officially classified robbery cases but in only about half of classified robbery killings. B. Patterns of Robbery Killing Two preliminary points merit mention before more detailed analysis of patterns of robbery killing can proceed. First, the divergence of patterns of robbery killing from those of robbery, noted in Tables 2 and 3 , is the most conservative estimate available on this data, as the tables deal only with officially classified robbery killings. Adding initially unclassified cases that were regarded as probable or possible robberies in the rerating exercise does not appreciably modify the contrast between patterns of reported robbery and robbery killing. 18 Second, the sharp contrast between patterns of lethal and nonlethal robbery events is arguably attributable to the differential dangerousness of various types of robbery. On this view, the fact that residential robberies account for 36 percent of all deaths but only 8 percent of nonlethal robberies is testament to the greater dangerousness of residential robbery. Attributing all noted differences in death to dangerousness would produce a provisional estimate that residential robbery is twelve times as dangerous as street robbery.' 9 An alternative interpretation would stress differences in reporting to and by the police as the major explanation of the sharp divergence of the patterns. A proponent of this view would stress the selective nature of victim reporting and police classification that feeds into the construction of patterns of officially noted nonlethal robbery. That only one out of ten nonlethal robberies involves a victim who might know his offender results from (1) victims' being less likely to report potential robberies to the police if they know the offender 20 and (2) the natural tendency for police to classify violent conflicts among acquaintances as something other than robbery when victims do complain. B. Patterns of Robbery Killing Our own view is that both the dangerousness and reporting hypotheses are partially correct. This in turn complicates the task of appropriately analyzing the differences officially noted. B. Patterns of Robbery Killing The drug-related robbery killing illustrates the problem of differentiating between dangerousness and reporting explanations. Approximately one in six officially classified robbery killings involves strong circumstantial indications that the lethal event was drug connected, either because the victim was known as a drug dealer, the offender was active in drugs, or drugs were present at the scene. B. Patterns of Robbery Killing 2 ' This figure compares with a negligible number of officially reported nonlethal robberies. 22 Are robberies involving illicit drugs more likely to lead to the death of the victim? We believe the answer is yes, because the much higher proba- 19 The following formula is used to determine relative dangerousness: 2' The figures for each of the variables in the robbery killing cases are in Appendix Table A3 . A case was considered to have drug involvement if there was an affirmative or probably affirmative response to any of the three questions. The one-in-five figure probably underestimates drug involvement since the drug activity of offenders and the presence of drugs at the scene is unknown in a large proportion of these cases. 22 22 In only one of 360 cases was drug involvement indicated in the police report. 22 bility that victim knows offender may motivate a killing to avoid detection or revenge, and because violence is commonplace with illegal drug traffic. It would be a mistake, however, to say that the absence of noted drug involvement in nonlethal robbery statistics means such incidents rarely occur. Victims involved in illicit drugs would not be expected to report offenses to the police, especially when the object of robbery is the illegal commodity itself. The absence of reported nonfatal drug robberies simply tells us that official statistics cannot be used to estimate the frequency of nonlethal drug robbery. 22 Thus, the high volume of drug-related robbery fatalities provides evidence that drug robbery is more life threatening than other robbery events, but we lack any basis for estimating the frequency of drug rip-offs and therefore the extent to which drug robberies are more dangerous. Further, and of significance, the presence of the drug cases in the killing sample may invite misleading inferences when all killing cases are compared with nonlethal robbery. The fact that drug-related robbery killings are reported and nonlethal drug offenses are not included in robbery statistics tends to inflate the apparent death rate of all robbery events and of other specific types of robbery. 22 The problem of confounding differences in dangerousness with the underreporting or different classification of nonlethal events is substantial for two other major categories of potentially lethal robberies previously mentioned: those where the victim knows his offenders and robberies occurring in residential settings. In each case, it is plausible to suppose that the death risk associated with robbery events is higher than with the prototype street robbery, but comparing patterns of officially reported nonlethal robbery with robbery deaths is an inappropriate way of estimating differential dangerousness. 22 The factors associated with nontypical robbery killings-prior relationship, residential setting, and drug involvement-frequently occur together, as shown in Table 4 . The locations associated with most nonlethal robbery, commercial and street settings, rarely lead to killings when the victim knows the offender or where there is strong evidence of drug involvement. 22 2 3 This pattern of clustering persists when those motiveunknown killings that were reclassified as probable or possible robberies are added. 24 23 Drugs are suspected of being involved in only one of the commercial robbery killings and only two street robbery killings. Some prior relationship between the victim and offender is indicated in 18 percent of the commercial killings and in 21 percent of the street killings. 24 24 See Appendix Table A4 . When a robbery involved more than one offender or victim, the offenders or victims or both were ranked by degree of involvement. For Table A4 , the most involved offender was compared with the most involved victim. NoTE.-Totals may not equal 100 due to rounding. 24 The strong association between the location of a robbery killing and factors such as prior relationship or drug involvement provides a method for comparing fatal and nonfatal robbery events that partially controls for the biases introduced by the selective nonreporting of nonlethal robbery events. While many of the factors associated with different patterns of robbery killing are frequently not known, the location of the robbery event can usually be unambiguously determined. It should be possible, then, to make specific comparisons between fatal and nonfatal robberies where nonlethal events are frequently reported and to avoid the substantial biases introduced when other categories of robbery killing are included in aggregate totals. 24 Our first excursion into the use of location-specific estimates concerns the death rate from robbery. Earlier attempts at estimating a death rate, using total robbery deaths and an overall figure for nonlethal robberies, included a substantial margin of error because of killings that might have been robbery related and were not so classified by the police. Specifying the location of robberies narrows the margin of error substantially, as shown in Table 5 . The death rates estimated in the table differ from earlier aggregates in three respects. First, the deletion of residential robbery killings lowers the rate of estimated robbery killing for nonresidential robbery. Second, the absence of questionable cases in commercial locations allows an estimated death risk for this category with a relatively small margin of error attributable to death classification problems. For street robbery, the large gap between minimum and maximum estimates persists, but the breakdown by location confirms that this problem is inherent in the data rather than attributable to inappropriate classification. Third, and most striking, the specific death rate from commercial robberies is about eight times that estimated for street robbery. Social Distance and Robbery Killing. The popular conception of robbery and of robbery homicide imagines a substantial social distance between victim and offender. Most homicide grows out of the victim's relationship with acquaintances and intimates. In theory, a potential victim's social status and choice of acquaintances has a significant effect on victimization risks. But the frightening collateral message of robbery as a stranger crime is that who one is or whom one knows is less important in determining chances of victimization. 24 We have already reported on one element of the social distance between victim and offender in robbery killing, the existence of a prior relationship between the victim and offender. This section uses alternative indicators of social distance between victim and offender for robbery killings subclassified by the location of the event. Table 6 launches the analysis by summarizing the frequency of nonstranger relationships between victim and offender and three other possible indicators of social distance between robbery and victim by the location of the robbery leading to death. 24 None of the factors reported in Table 6 is an unambiguous indication of social distance, but all seem relevant to the concept as it is usually understood. The aggregate picture both confirms the image of robbery as a crime generally involving social distance and suggests that that perception needs significant qualification. Seven out of ten killings involve a victim with no prior relationship to the offender and two out of three involve a victim and offender more than ten years apart in age. Yet three quarters of our homicides involve a victim and offender of the same race and eight out of ten involve males as both victim and offender. With respect to sex and race, these findings suggest that robbery killing victims are disproportionately selected from Chicago's population to match the race and sex of the offender. Cross-tabulating measures of social distance by the location of the robbery produces a clearer picture. Residential robbery killings produce low values of social distance between victim and offender: a majority of these events involve nonstrangers, and eight out of ten do not cross racial lines. Commercial robbery killings, by contrast, involve strangers four-fifths of the time and cross racial lines in 43 percent of the cases where the offender's race is known. 24 Killings generated by street robbery occupy a middle position in measures of social distance. When the analysis is confined to police-classified robbery killings, a quarter of all victims know the offender, and approximately the same proportion of cases involve victim and offender within ten years of each other in age. These findings are consistent with substantial social distance between victim and offender in most cases. Almost all of the street killings, however, involve male victims and nine out of ten involve a victim and offender of the same race, a pattern that indicates that the risk of robbery death is not distributed randomly throughout the 25 community. 24 2 Adding probable and possible robberies to the street and residential robbery killings tends to decrease the estimated social distance between victim and offender. Weapon Use and the Robbery Death Rate. A striking example of the importance of location-specific comparisons concerns the question whether the weapon used in robbery affects the chance that a victim death will result. Table 7 , comparing all officially classified robbery deaths and 25 According to the 1980 census, the racial composition of Chicago was 40 percent black, 14 percent Hispanic, and 46 percent white and other. The nonfatal robbery sample in our study included 69 percent blacks, 10 percent Hispanics, and 22 percent whites and others. 24 26 See Appendix Table A5 . our sample of robbery events, gives the impression that the choice of weapon has no influence on death rate. Robberies involving only personal force account for 35 percent of nonlethal offenses but only 7 percent of all fatalities. The death rate from such events is approximately one tenth that of robberies committed with guns, knives, or other weapons. But the death risk associated with all weapon types (measured by dividing a particular weapon's share of death cases by its share of nonlethal cases) seems indistinguishable. 27 Thus, whether or not a weapon is used in a robbery is a major influence on the death rate, but it appears that the choice of what specific weapon has no further influence on the risk of fatality. 24 This finding is inconsistent with the scant prior research on the question of weapon dangerousness. 24 2 8 The lack of differential between weapons is also a demonstrable artifact of including residential cases (without a substantial representation in the nonlethal sample) and aggregating all robbery types into a single category. Table 8 separately compares fatal and nonfatal robberies for street, commercial, and other locations using the same data as employed in Table 7 . Shootings dominate the robbery death statistics by specific location, ranging from two-thirds of all street robbery killing to more than 80 percent of the commercial and other location robbery deaths. The ratio of killings to nonlethal robberies discussed in the previous paragraph estimates a death rate per hundred gun robberies more than twice as high as 27 The death rate per thousand robberies associated with use of each type of weapon is 1.9 for guns, 2.1 for knives, and 1.7 for other weapons. The death rate associated with personal force is only .14. the death rate for knife robbery in street and other robbery locations. 29 The flat pattern in the aggregate totals obtains because a third of all residential robbery killings were committed with knives, whereas only three of the twenty-seven reported nonlethal robberies occurring in nonresidential settings involved a knife. If residential robbery killings are excluded from the sample, guns account for 76 percent of robbery deaths. Using the full year statistics on reported robbery for 1983, guns accounted for 27 percent of classified robberies. Knives account for 13 percent of robberies and 12 percent of robbery deaths. This produces a restated estimate that gun robberies known to the police (excluding residential cases) are three times as likely to result in death as robbery committed with knives, the next most dangerous weapon in these statistics. 29 As previous work has shown, estimates of weapon dangerousness based only on reported cases tend to underestimate the lethality of guns compared to other weapons because a higher proportion of nonlethal gun robberies are reported to and by the police. One previous study has suggested that the extent to which gun robberies are more dangerous than knife robberies is at least three to one when estimates of weapon use in nonlethal robberies are taken from victim surveys rather than police statistics. 30 The location-specific estimates developed from this study are consistent with these earlier approximations. 29 In street locations gun robberies are 2.3 times more lethal while in "other" locations they are 2.2 times more lethal. 29 30 Zimring, supra note I, at 325. Gender, Resistance, and Robbery Death Risk. Another topic on which location-specific comparisons prove useful is the relationship between the victim's sex and the death risk from robbery. Table 9 provides the pertinent data. 29 Female robbery victims range from 28 percent of all reported street cases to 45 percent of the small and problematic sample of nonfatal residential robberies. Robbery killings, however, involve male victims predominantly. Excluding residential robbery killings, female victims are rare: 7 percent of commercial robbery homicides, 11 percent of other location robbery killings, and 6 percent of the street robbery killings in Chicago during a twelve-month period. 29 One method of analyzing these patterns is to estimate the relative death risk of robbery for each sex using the frequency of fatal and nonfatal events, the approach used in our discussion of weapon dangerousness. By this method, commercial robberies with female victims result in death at less than an eighth the rate of commercial robberies with male victims. Street robbery, with only one female fatality, is six times less deadly than male victim street robbery, and other location robberies involving female victims are also about one sixth as deadly as those with male victims. Much of the difference by gender is related to differences in perceived and actual victim resistance. Robbers may think that women are likely to offer less resistance to robbery and thus they will use less force at the outset of a robbery. Further, the large difference in death rate by sex and the persistence of this pattern in gun robbery suggest that actual resistance is much less frequent among female robbery victims. 29 3 ' Table 10 introduces the analysis of resistance and robbery death by showing the pattern of resistance for robberies and robbery killings. The robbery event was classified into one of three categories: no resistance noted, passive noncooperation (the victim usually says he or she has no money), and active noncooperation (including refusal, flight, and physical force). Loss of life in robbery is strongly associated with active victim resistance. Only 8 percent of the robbery cases resulted in this classification compared with 55 percent of the death cases. Put another way, active noncooperation is associated with a death risk from robbery approximately fourteen times as great as cooperation or passive noncooperation. Passive noncooperation is about twice as likely to produce a lethal outcome as no resistance in our data. This pattern holds when the cases are separately analyzed by robbery location. The resistance estimates discussed above are based on robbery cases reported to and by the Chicago police. Because successfully resisted robbery attempts are less frequently reported to the police by victims, the difference in death rates between active resistance and nonresistance cases may be overstated. 29 An imperfect method for correcting nonreporting biases using victim survey data confirms the large difference in death risks associated with resistance. The comparison is imperfect because the survey data exclude commercial cases, fail to distinguish between active and passive resistance, and include many incidents of ambiguous seriousness. 29 3 3 For gun robbery attempts in the victim survey, a total resistance rate (active and passive) of 24 percent is reported by Block and Block. 29 34 Using this esti-32 Active resistance accounted for 82 percent of commercial robbery killings but only 8 percent of the general robbery incidents in commercial settings. Active resistance was present in 54 percent of all street robbery killings but only 9 percent of street robberies. Street robberies involving active resistance were estimated to be sixteen times more likely than nonresistance cases to end in the death of the victim. The multiple for commercial cases, involving a sample of only eleven killings, was wfoster@example.com. 29 33 See Block & Block, supra note 9. 29 mate of resistance, the death rate from gun robberies involving undifferentiated resistance is 8.6 times the level found in nonresistance cases. 29 3 5 29 Finding active resistance associated with a much higher death risk is not the equivalent of proving a causal relationship between the victim's resistance and increased risk of death. In some cases, the lethal intentions of the robber may provoke an otherwise passive victim rather than that the active resistance transforms the robber's intent. Our inability to make confident assessments of the sequence of resistance in the killing caseswhether resistance altered or resulted from the offenders' intentions to injure-limits our ability to estimate with precision how many additional deaths are generated by victim resistance. 29 But our current data suggest the independent role of resistance is substantial. Even if half of all robbery killings associated with active resistance would have occurred in any event, active resistance would still escalate the risk of death by a factor of between three and four. 29 36 Under such circumstances, prudent victims should avoid most active noncooperation when involved in armed robbery. And the strong relationship between victim's gender and the death risk from robbery is further circumstantial evidence that resistance provokes higher death risks in armed robbery. C. Robbery with Injury Between the high volume of robbery events that do not injure and the relatively small number of robberies that kill there are a substantial number of cases that produce physical injuries in their victims of various degrees of seriousness. Unlike the robbery killing and police-classified robbery event, there is no special category in official statistics for robberies causing physical injury to the victim. Surveys of victims of violent crimes have provided some data on the incidence and correlates of robbery producing nonfatal injury, but the phenomenon remains understudied. 37 35 Thirty-three deaths resulted from gun robberies with undifferentiated resistance, twelve deaths where no resistance was involved. If the 24 percent resistance estimate is applied to nonfatal gun robberies, the ratio is thirty-three with resistance to 103 without. 33 =86 12 103 36 The precise estimate depends on the choice of method. Eliminating passive resistance cases, and transferring half of all active resistance deaths to the no resistance category. produces an estimate that resistance cases are 4.7 times as likely to cause death as the no resistance robberies. This research provides two data sets on the incidence and distribution of robbery with injury. Our sample of police-classified robberies, thirty cases per month for the study year, provides some cases of robbery leading to injury and an estimate of the prevalence of physical injury in police-classified robberies. Table 11 sets out this distribution. The base rate of injuries leading to hospital attention is low, 10.2 percent of our sample of classified robberies. The distribution of injuries in robbery events also seems skewed toward the less serious end of the spectrum: only 19 percent of all injury robberies as we define them probably resulted in hospital admissions, ambulance calls, or other indications of serious wounding, a rate per hundred robberies of 1.9. =86 12 Because the rate of robbery injuries is relatively low, and skewed toward non-life-threatening cases, we collected a supplementary sample of robberies that led the victim to seek hospital care or otherwise showed indications of seriousness. The first thirty such cases in a month were selected by the Detective Division of the Chicago Police Department for inclusion in this sample. 38 Our sample uses a broad definition of victim injury. Only one in five of the injury cases was regarded as unambiguously serious. For this reason, it is important not only to make comparisons between noninjury and injury robberies but also to contrast those robberies producing some injury with the minority of robbery injury cases that require hospital admission. Table 12 provides the distribution by location of robberies, robberies with injuries, robberies with injury requiring hospital admission, and robbery deaths. Each robbery location has its own distinctive pattern as comparisons proceed from all robberies through degrees of injury to fatalities, from left to right in the table. Robberies in residential settings, one out of twelve police reported robberies, are involved in only one out of every twenty robberies with injury. When injuries do occur, they are more frequently associated with the serious cases, accounting for 7 percent of the hospital admission and ambulance cases in our sample. With 38 Incident reports filled out by Chicago police whenever a crime is reported include a box to be checked if a victim is taken to a hospital. Only reports so checked were included in the supplementary sample. Copies of all robbery incident reports are sent from the field to the Crime Analysis Unit of the Detectives' Division at the police department's central headquarters. There they are reviewed by a detective knowledgeable about robberies who searches for patterns to bring to the attention of field personnel. At the beginning of each month, this detective selected for inclusion in our supplementary sample the first thirty cases he examined where a check indicated that the victim had been taken to a hospital. The reports came in small batches from the field offices and were examined by the detective in the order received. Since it took a number of days for the sample to be completed each month, it is likely that this convenience sample approximates a random one quite closely. that exception, the proportion of officially reported nonfatal robberies involving residential locations does not increase when injury or serious injury cases are isolated, and the percentage of residential cases never approaches the 36 percent of robbery killings associated with residential settings. Commercial robberies, responsible for I I percent of the main sample of nonlethal robbery events, account for less than half that proportion of robberies with injury and no reported cases of serious injury in our sample. Unlike nonfatal residential robberies, commercial robberies are usually reported and classified as such. Such robberies apparently involve behavioral dynamics and weapons that generate substantial death risks but small risks of injury. 39 '9 The importance of weapon use is supported by Appendix Table A6 , which demonstrates that injury cases in commercial settings as in other settings generally occur where guns are absent. 39 Street robbery, by contrast, is associated with relatively high risks of injury and low risks of death. Street incidents account for half of all reported robberies, two-thirds of the robberies with injury and hospital admission cases, but only 20 percent of the deaths. This pattern is unlikely to result from reporting difficulties. Adding in all possible street robbery killings still leaves us with street robberies responsible for twice the proportion of robbery injuries as of robbery deaths. 4°T able 13 reports the distribution of robbery, robbery injury, and death cases by race and sex of victim. White victims with other than Hispanic surnames account for one-fifth of noninjury robberies, a quarter of robbery injuries, only 15 percent of the hospital admission cases, and 26 percent of the deaths. The somewhat higher proportion of white victim cases in the death category is attributable to the high death rate and low injury rate associated with commercial robberies, a category that includes a majority of the white victim deaths in Chicago. 39 4 ' Black victimization accounts for at least 60 percent of the robbery cases in each category of victim harm, with higher concentrations among the hospital admission group than the other injury or death cases. Hispanicsurname victims experience a larger relative frequency of robbery injuries than either noninjury robberies or robbery deaths. 42 Two aspects of the pattern of victimization by sex merit special attention. First, male victims outnumber female victims in reported robberies by a two-to-one margin, and all that is known about probabilities of reporting to the police suggests that this is certainly no artifact of sex-based reporting. This two-to-one difference in robbery victimization roughly doubles again with respect to the incidence of injury or death, where the difference in risk between the sexes approaches four to one. Adding information on two categories of nonlethal injury thus underscores the strong difference in risk of aggravation by sex noted earlier. Table 14 provides the distribution of weapons used across the spectrum from uncomplicated robbery to robbery killing. Guns dominate robbery killings statistics and account for a plurality of uncomplicated robberies as previously noted and discussed. 4 3 Gun cases are underrepresented in the robbery injury sample, consistent with previous studies, but show up more than twice as often in the most serious category of robbery injuries. 42 4' Adding all possible street robbery killings increases the percentage of street killings to 24 percent. 41 See Appendix Table A6 . 42 Our first guess was that Hispanics would be overrepresented in street robberies, but this turns out on further examination not to be the case. The percentage of robberies taking place in street settings is 56 percent Hispanics, 48 percent whites, and 58 percent blacks. 42 43 See Table 7 and accompanying text, supra. Knives account for the same proportion of robberies and robbery injuries, 14 percent, and one-fifth of the serious injury and death cases. Removing residential robbery deaths to provide for continuity across the samples reduces knife killings to 10 percent of the total. Robberies without weapons account for more than a third of all events, more than half of all injuries, and 31 percent of even the hospital admission cases. A sharp drop-off occurs in the transition from hospital admission cases to recorded fatalities. 42 A summary statement of the relationship among the various robbery harm categories would emphasize three elements: (1) the overlap between patterns of nonlethal robbery without injury and those leading to injury; (2) the sharp differences between robbery killings and nonlethal robberies; and (3) and robbery injury cases. Figure 2 attempts to visually portray the noted relationship among these three categories. 42 The profile of robbery injury cases closely follows general patterns of nonlethal robbery: there are more male victims, more street cases, and fewer guns, but the two samples are similar in most other respects. In contrast, half of all robbery killings involve situations and locations not frequently found in nonlethal robbery. The sharpest disjunction in pattern occurs when robbery injury cases are compared with reported cases producing robbery victim deaths. D. Groups and Robbery Outcome The information available about offenders in this study is limited by low clearance rate for nonfatal robbery. On one issue, however-the number of offenders involved-a fair if imperfect comparison between lethal and nonlethal robbery is permitted by the higher clearance rate associated with the killings and the accuracy of victim reporting in the nonfatal cases. Table 15 presents a distribution of robbery cases by number of offenders involved, for robbery killing, robbery with injury, and robbery. D. Groups and Robbery Outcome The table makes two points. First, robbery of all kinds is a group offense. Less than 40 percent of robbery events in our sample, regardless of outcome, involve a lone offender. Second, there are no clear indications of significant differences between robbery, robbery injury, and robbery killings in the relative concentration of group offenses. Table 16 attempts to take this analysis one step further, by reporting the percentage of cases with more than one offender on a location-specific basis, deleting the problematic residential category from the analysis. Table 16 is superior to the initial analysis because it reports the group participation for each separate location. To make this possible, however, we must divide robbery events into individual and group to avoid the problem of insufficient numbers. D. Groups and Robbery Outcome And even with the compression of cases into solo and group categories, the number of commercial cases in each category is insufficient for confident statistical analysis. Still, the preliminary indications with respect to the commercial cases deserve mention. Less than a third of the robberies without victim injuries involve more than one offender, and more than three-quarters of the commercial robberies involving significant victim injury or victim death are group related. D. Groups and Robbery Outcome Larger samples will be needed to confirm whether this pattern is significant. Intuitively, it might make sense: commercial establishments are frequently in a better position to defend themselves from robbers than individuals in street or other locations. That is one reason successful commercial robberies more frequently involve guns. The lone robber may frequently be at a disadvantage relative to the target establishment, which diminishes his capacity to injure or kill his victim. D. Groups and Robbery Outcome The lessons of Table 16 are consistent and worthy of note. The presence of more than one offender is not associated with significant differences in the probability of victim injury or death. But the analysis of larger samples, cross-tabulating group involvement by weapon and dealing separately with constellations of two, three, and four or more robbers, may uncover significant differences lying beneath the apparent similarity. E. The Apprehension of Offenders: An Unresolved Puzzle This study was not designed to be a detailed investigation of the factors that produce arrests for robbery, and our capacity to illuminate the process of police work in robbery cases is extremely limited. Within these limits, there is merit in examining what data we have to highlight issues that future research should address. E. The Apprehension of Offenders: An Unresolved Puzzle We begin (in Table 17 ) with the overall figures on clearance by the police for robbery, robbery with injury, and robbery killing. 44 The general pattern is clear, if not easily explained. Approximately one of every ten robberies reported to the Chicago police is listed as solved within two months of the event. There is no significant difference between clearance rates for unaggravated robberies and for those resulting in injury to the victim, but the clearance rate for robbery killing is five times as great as for other robbery. This dramatic difference in clearance rates is the focus of the analysis that follows, in which we attempt to explain the distinction, largely without success. 44 Earlier sections of the study show the disjunction between patterns of robbery killing and patterns of reported nonlethal robbery. Seeking some of the explanation in the different representation of various types of robbery in the killings cases seems a logical next step, as shown in Table 18 . 44 The two striking elements of the table are the evenness of pattern for clearance rates for all types of robbery killings and the consistency in the sharp contrast between fatal and nonfatal robbery. Since residential rob-" Clearance rates can be measured in several ways, depending on whether they include only cases that resulted from police investigation, or in addition either cases reclassified from robbery to some other crime or cases that were considered unfounded. This figure represents the percentage of cleared cases by investigation as a percentage of those cases determined by investigation to have actually involved robberies. bery killings contain a larger proportion of the special patterns discussed earlier, the even
{'paper_id': '56250716', 'title': 'Victim Injury and Death in Urban Robbery: A Chicago Study', 's2_url': 'https://api.semanticscholar.org/CorpusID:56250716', 'source': 'S2ORC'}