HOMICIDE: BEHAVIORAL ASPECTS

Homicide is the killing of one human being by another. As a legal category, it can be criminal or noncriminal. Criminal homicides are generally considered first-degree murder, when one person causes the death of another with premeditation and intent, or second-degree murder, when the death is with malice and intent but is not premeditated. Voluntary manslaughter usually involves intent to inflict bodily injury without deliberate intent to kill; involuntary manslaughter is negligent or reckless killing without intent to harm. Noncriminal forms include excusable homicide, usually in self-defense, and what is called justifiable homicide, as when a convicted offender is executed by the state. The classification of any homicide as either criminal or noncriminal, or of a death as either a homicide, an accident, or a natural death, is not the same in all time periods or across all legal jurisdictions. What is considered a homicide death varies over time by the legal code of given jurisdictions and by the interpretations and practices of agencies responsible for reporting deaths. When cars were first introduced into the United States, for example, deaths resulting from them were classified by some coroners as homicides, although now they are generally labeled accidental unless caused by negligence. An abortion may be considered a criminal homicide or the exercise of a woman's reproductive choice. Homicide statistics, like those of many other crimes, reflect definitions and legal interpretations that vary over time and space. Agencies responsible for reporting deaths influence how a death is reported. Roger Lane describes, for example, that coroners in early twentieth-century America were paid to determine the cause of deaths on a feefor-service basis. The same fee was paid no matter how difficult the case, and in some cases, the fee was collected from the convicted offender. In difficult cases or those for which the coroner might not expect payment, as when a newborn was killed by an indigent woman, the cause of death might be reported as suffocation of the infant rather than as a homicide. Criminal homicide reflects the political processes that affect all definitions of crime.

Sources of data on homicide

Homicide data generally derive from either health or police agencies. There are two major sources of international data; one complied by the United Nations in World Health Statistics Annual and the other by the International Criminal Police Organization (Interpol), which was established in 1950. The national police agency of each country reports the number of that country's homicides for every two-year period. World Health Statistics Annual publishes the cause of death, including homicide, for each reporting country. These statistics, which have been collected since 1939, are the joint product of the health and statistical administration of many countries and the office of the United Nations and the World Health Organization. Problems in the use of these sources include lack of consistent definitions and interpretations across jurisdictions and lack of consistent reporting by all countries. Some countries, including most in Africa and many in Asia, do not routinely report (LaFree). Furthermore, there are few validation procedures to assess the accuracy of the data. For a summary of difficulties with these data sources, see LaFree.

Within the United States there are two major national sources of data on homicide: the National Center for Health Statistics (NCHS) and theFederal Bureau of Investigation Crime in the United States (known as the Uniform Crime Reports, which is published annually). The NCHS data derive from coroners and medical examiners, who forward death certificates to the center's Division of Vital Statistics. These data focus solely on the homicide victim and generally include information on the cause of death and the age, race, and sex of the victim. Data about offenders, victim offender relationships, and motives are not included. The various states entered this national reporting system at different times. Prior to the 1930s, when the system became fully national, the data available depended on which states and cities were included. Boston was the first entrant, and in general there were data from the East Coast cities very early. Boston had death data in 1880, Pennsylvania in 1906, and Washington, D.C., in 1880. Other states, such as Georgia and Texas, entered the registry much later—in 1922 and 1933, respectively. In establishing trends, then, there is difficulty in obtaining national data before 1930.

The Uniform Crime Reports, a voluntary national data-collection effort, began in 1930 and gradually accumulated reporting police districts. Homicide reports are detailed and include information on both victims and offenders and, since the 1970s, on victim-offender relationships. This system is the only national one with information on homicide offenders and includes information on crimes classified by size of population, state, county, and Standard Metropolitan Statistical Area. Although there are some problems with the use of the Uniform Crime Reports data, they are commonly used in studies of homicide.

In general, information on the number of homicides in the nation reported by NCHS and the UCR show relatively high agreement. However, there is variation, sometimes substantial, when comparing the two sources on such questions as age or ethnic background of the victim. A discussion of these differences are found in Riedel.

Although the UCR and NCHS are the most commonly used national data sources for studies of homicide, the National Incident Based Reporting System (NIBRS), which is under development, may become an important source in homicide research. This system originated as a result of the 1982 F.B.I. Bureau of Justice Statistics task force comprehensive evaluation and redesign of the UCR program. When fully implemented there will be more detailed data at the national level than are currently available (Reidel).

In addition to these national sources, researchers have records of specific homicide cases, available either from medical examiners' offices or from police departments. Such records are richer in detail than those at the national and international levels and provide more specific evidence on time and location of homicides, alcohol and drug involvement, sequence of events leading to victim-offender confrontations, and the like. Locally based data can be used to augment those compiled nationally and are useful for describing homicide events in detail. There is extensive long-term city level information available from police records in Chicago (Block), St. Louis (Decker, 1993; Rosenfeld), Philadelphia (Wolfgang; Zahn, 1997) as well as other cities. These data are available in analyzed form from the publications of the authors, and are also available from the Inter-University Consortium for Political and Social Research (ICPSR) at the University of Michigan and at their web site (http://www.umich.edu). Most of these studies rely on the model established by Marvin Wolfgang in his classic study Patterns in Criminal Homicide (1949).

Cross-national patterns of criminal homicide

Although there are problems in using international crime statistics because of differing definitions and methods in classifying the phenomenon, both Interpol and the United Nations data nonetheless offer useful information on homicide rates in different countries. Crossnational studies of homicide are generally based on either WHO or Interpol data. There are a number of problems with these sources including lack of representation of many countries (e.g., Africa, Asia, former Communist countries). Lack of consistency in reporting is also a problem. Gary LaFree, in summarizing these problems, supports an earlier assessment by Kalish, who said, "It is risky to quote a crime rate for a particular country for a particular year without examining rates for other years, and, whenever possible, rates from other sources" (quoted in La-Free, p. 138).

Despite these difficulties, studies confirm that, in general, Central and South American nations have high rates of homicide. In fact, Colombia is frequently the nation with the highest homicide rate. Also, several former Soviet block nations tend to have high homicide rates, notably the countries of the Russian Federation. Countries with the lowest homicide rates tend to be Western European nations. Japan often has the lowest rate of homicide. Again, it is important to note differential reporting from some areas of the world. There is only one African nation that has somewhat consistent reporting to the WHO from year to year (Mauritius). Few Asian countries, including the Middle Eastern countries, are represented. Table 1 shows worldwide homicide rates drawn primarily from the World Health Organization.

Researchers have tried to explain why there are differences in rates between countries. In his summary of these studies, LaFree notes several explanations. The most consistent finding is that the greater the difference between the rich and the poor in a country, the higher the country's homicide rate. Some research shows that the difference between the rich and poor has a stronger effect on homicide rates in areas that are densely populated. However, it does not appear that the number of people unemployed in a country or the degree of population density alone is related to its homicide rate. It is important to emphasize that the difference between the rich and poor groups in a country, in terms of income and education, has the most effect on a country's homicide rate.

Another explanation for differences in homicide rates is the varying levels of economic development across nations. Economic development refers to, for example, the per capita gross national product, the number of telephones, radios, or newspapers in a country, the amount of energy used, and the amount of industry and technology in a country. Most research shows that the less economic development in a country, the higher its homicide rate. For example, Japan is an economically developed country, as are many Western European nations, and they have low homicide rates. The obvious exception to this generalization is the United States, which is highly developed economically but also has a high homicide rate. Reasons for this exception are not clear, although patterns of gun ownership by individuals may have a bearing on it.

Other explanations for differences in national homicide rates relate to the makeup of a country's population. Some researchers suggest that the number of teenagers and young adults in a country is related to higher homicide rates, but findings are inconsistent. Other studies contend that the number of different linguistic, racial, ethnic, or religious groups in a country influence the homicide rate. However, there has been little evidence showing that a greater number of such groups are related to higher homicide rates. One relationship that has been consistently associated with homicide rates is increasing population growth. The faster a country's population is growing, the higher its homicide rate tends to be.

Patterns of criminal homicide in the United States

While comparative studies have focused on the broad question of rates of homicide, studies in the United States examine how the rates change through time, which groups are affected, and the relationships between victims and offenders. Zahn and McCall summarize national homicide trends in the twentieth century. While national data from the early twentieth century are not readily available, they conclude that the homicide rate increased moderately between 1900 and 1933. After the mid-1930s, when data are more reliable, rates dipped sharply then rose between 1933 and 1974. The rates declined through 1964, although this decline was briefly interrupted by a short increase in the three years after World War II. After 1964, the rates began to rise from 6.1 per 100,000 in 1967 (UCR), to 9.7 in 1974, to an all-time high of 10.2 in 1980. Overall, the United States homicide rate doubled from the mid 1950s to 1980. After 1980, the homicide trend fluctuated, dropping to 7.9 in 1985, going up to 9.8 in 1991, and then decreasing through the late 1990s. In 1998, the UCR reported a homicide rate for the United States of 6.3, which represents the lowest U.S. homicide rate since 1967. In general, the highest homicide rates of the twentieth century in the United States occurred during the 1970s, 1980s, and early to mid-1990s, whereas the lowest rates occurred during the late 1950s.

There are consistent differences in rates of homicide victimization between males and females, blacks and whites, and young and old. In terms of age difference, homicide victimization rates are generally higher for young adults, especially young adult males. In the past, the highest rates have occurred for the age group twenty-five to thirty-four, followed by fifteen to twenty-four year olds. In the 1990s, the rates for most age groups declined, but the rates for these two groups continued to increase. By 1989, the fifteen to twenty-four-year-old group converged with and then surpassed the twenty-five to thirty-four-year-old group. In 1993, the homicide rate for fifteen to twenty-four year olds was 23.5 per 100,000 (Vital Statistics ) and 19.5 for the twenty-five to thirty-four year olds. Zahn and McCall, who summarized these trends, point out that shift in the age structure of homicide is one of the most important changes in the patterns of homicide during the twentieth century.

Reynolds Farley has reported that ageadjusted homicide rates during the period 1940–1977 were about six times greater for men than for women. Race and gender-specific victimization rates from vital statistics from 1968 to 1997 confirm this, with a black male rate of 47 per 100,000 in 1997, compared to 6.7 per 100,000 for white males. (The rate for black females in that year was 9.3 and for white females 2.3.) Explanations for why racial minorities are overrepresented as both victims and offenders of homicide have focused on income inequality between racial groups as well as racial segregation in housing. Segregation into areas with few economic resources may lead to frustration and hostility that increase violence. Such isolation may also undermine the ability of the community to mobilize community residents for crime prevention activities (Peterson and Krivo).

The low rates of victimization and offending for women as compared to men are not adequately explained. Differences in social inequality do not seem to be as important, and various studies have confirmed that there has not been a great escalation of female homicide rates accompanying women's increased participation in the labor force in the United States. While males dominate as victims and offenders when considering the homicide rate overall, gender patterns differ greatly in reference to a specific type of homicide, intimate partner homicide. Only in the area of partner homicides do women's offending rates approach that of men; even here, however, women are twice as likely to be killed by their partners as men are by their female partners. Women are more likely to be killed by their male partners than by any other assailant. A substantial majority of homicides committed by women occur in response to male aggression and threat. Other studies show a history of physical abuse and threat by men who eventually kill their victims. It is clear that the link between partner separation and murder is more than incidental, such that when a woman leaves a man he experiences rage that leads to her murder. A summary of research on homicide between intimate partners is found in Browne, Williams, and Dutton.

Victim-offender relationships

Although many relationships occur in human affairs, only some seem to be persistently associated with homicide in the United States. For example, an employee-employer relationship is less frequently associated with homicide than a husband-wife relationship. Unfortunately, information concerning the relation between the victim-offender and reasons for the murder are often difficult to obtain. Each homicide event can be characterized by motive. The descriptions of the motive or of the events by the participants may differ from those of official agencies or of researchers. Definitions used by some researchers for friends, acquaintances, or strangers are sometimes not specified, thus making it difficult to compare various studies of victim-offender relationships. Despite such difficulties, comparisons show that in early U.S. history the major type of homicide in both the North and the South was that of a male killing another male with whom he was acquainted, while they were in a nonwork setting (Lane). In the 1920s and 1930s, homicides that resulted from criminal transactions or justifiable homicides by police, often related to bootlegging and prohibition laws, became more prominent (Boudouris; Lashly).

In the 1940s and 1950s, homicide rates were relatively low and stable. Two types of homicide were most prevalent: homicide between family members, usually husbands and wives, and homicide between two males known to each involved in an argument. From the 1960s into the 1990s, UCR data indicate that homicide between acquaintances and friends was the most predominant form, ranging from a high of 51 percent of the total in 1963 to a low of 34 percent in 1995. The percentage of homicides involving acquaintances dropped during this time, and since 1990 has been superseded by those where the relationship between the victim and offender is unknown. There has also been a decline in family-related homicide, varying from 31 percent of the total in 1963 to a low of 11 percent in 1995.

Based on Uniform Crime Reports, arguments are the predominant precipitating event in homicides, through time. However, in the 1970s and early 1980s there were many homicides in large cities associated with robberies, and in some large U.S. cities in the late 1980s and early 1990s, there was an upsurge of homicides related to narcotics trafficking. The number of homicides for which police do not know the precipitating circumstance showed the greatest increases in the last quarter of the twentieth century in the United States; despite this increase, the majority of homicides still involve victims and offenders who are acquainted.

The Technology of Homicide

Homicide is also characterized by technology, which includes implements used to kill (guns, knives, and clubs) and substances (drugs and alcohol) that may cause or contribute to the crime. The majority of homicides in the United States are committed with a gun, usually a handgun. Uniform Crime Reports in 1998 revealed 65 percent of homicides were committed with a firearm. This percentage has remained relatively constant since 1970. Knives are the second most frequent method used, claiming 13 percent of deaths in 1998. Rates of murder involving guns are higher in the southern regions of the United States and are increasingly prevalent in homicides involving teens and young adults (Fox and Zawitz, 2000). The extent to which gun control would affect the rate of homicide remains an issue of continuing debate. Some researchers suggest that the ready availability of guns in the United States is related to the nation's high rates of criminal homicide, while others suggest that factors associated with the willingness to use guns are also of importance.

There have been attempts to explore the relationship between homicide and the use of alcohol and drugs. Studies that examine alcohol use and homicide commonly examine the percentage of victims, offenders, or both who were drinking at the time of the fatal attack. Wolf-gang's study, for example, found that in 64 percent of the homicides in Philadelphia, either the victim or the offender had consumed alcohol. Although much of the literature shows some association between alcohol and homicide, the means by which this association occurs remains problematic. Parker and Auerhahn (1999) suggest that selective disinhibition explains the association. Alcohol impacts judgement, and in potentially violent situations, alcohol will disinhibit norms that constrain individuals from engaging in violent behavior—especially in situations in which violence is seen as likely to result in successful resolution of a dispute. While exact ways in which this occurs remains obscure, some researchers studying the connection suggest that alcohol may be one causal agent in the genesis of homicide. Most researchers agree that alcohol interacts with social contexts and social relationships; it alone, apart from social contexts, does not explain the occurrence of homicide.

The relationship between drugs other than alcohol and homicide poses many of the same problems. Paul Goldstein and colleagues suggested that drugs may be associated with homicide in one of three ways. First, drug use by offenders or victims may alter behavior and increase the likelihood of violence or victimization. Second, some drug users may engage in violent crime accidentally while committing relatively nonviolent crimes aimed at securing money to buy drugs. Third, homicide may be systematically related to the use of illegal substances in that it may involve conflicts between rival drug dealers over territory, settlement for "bad debts" or for "bad drugs," and the like. Studies dealing with the impact of each of these situations have been done, although which, if any, of the three contributes most to the drug-homicide relationship is unknown, since existing studies have produced contradictory results.

Sociological explanations of homicide

There are a number of sociological explanations for homicide. Most explanations have focused on explaining why rates of homicide are different in different groups, for example, minority versus majority groups, or in different regions of the United States, such as South versus North. Two major lines of thought, cultural and social structural, have been most prevalent. While these explanations are not mutually exclusive, debates between advocates of these perspectives have been common. Cultural theorists explain homicides as resulting from learned, shared values and behavior specific to a given group. The basic causes are in the norms and values, transmitted across generations, that are learned by members of a group. Certain subgroups exhibit higher rates of homicide because they are participants in a subculture that has violence as a norm. First developed by Wolfgang in 1958 and later expanded by Wolfgang and Ferracutti in 1967, this position asserts that there is a subculture of violence—that is, a subculture with a cluster of values that support and encourage the overt use of force in interpersonal relations and group interactions. The subculture is reflected in the psychological and behavioral traits of its participants. Ready access to weapons and the carrying of weapons are symbols indicating a willingness to participate in violence and to expect and be ready for retaliation. The development of favorable attitudes toward the use of violence in a subculture involves learned behavior and a process of differential association or identification. In general, violence is a learned shared mode of adaptation for specific groups of people (Wolfgang and Ferracutti).

Social structural explanations have been more pronounced in the 1980s and 1990s. The factors most commonly studied are two features of economic stratification: poverty and income inequality. Poverty refers to absolute economic deprivation wherein persons have difficulty securing the basic necessities for a healthy life, whereas relative deprivation refers to relative lack of material goods, on the premise that the subjective experience of deprivation motivates individuals to violence (Messner and Rosenfeld). Studies show that poverty alone is not consistently linked to homicide, although it is a related component. The inequality hypothesis has also been tested using different units of analysis, that is, neighborhoods, cities, and nations. For subnational units the evidence is somewhat mixed, and at the national level results are very consistent. Nations with high levels of income inequality tend to exhibit high homicide rates. Further refinement of research on the relationship between economics and racial and other forms of inequality needs to continue, as do attempts to integrate cultural and social structural approaches. Studies of factors related to specific types of homicide, such as intimate partner homicide and gang homicide, are also important and are proving more useful in suggesting ways to prevent such deaths than are the more general approaches.

Margaret A. Zahn

See also Assassination; Guns, Regulation of; Domestic Violence; Homicide: Legal Aspects; Suicide: Legal Aspects; Terrorism; Violence; War and Violent Crime.

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