During the twentieth century, the sociological approach to criminology became the most influential approach. Sociology is the study of social behavior, systems, and structures. In relation to criminology, it may be divided into social-structural and social-process approaches.

Social-Structural Criminology Social-structural approaches to criminology examine the way in which social situations and structures influence or relate to criminal behavior. An early example of this approach, the ecological school of criminology, was developed in the 1920s and 1930s at the University of Chicago. It seeks to explain crime's relationship to social and environmental change. For example, it attempts to describe why certain areas of a city will have a tendency to attract crime and also have less-vigorous police enforcement. Researchers have found that urban areas in transition from residential to business uses are most often targeted by criminals. Such communities often have disorganized social networks that foster a weaker sense of social standards.

Another social-structural approach is the conflict school of criminology. It traces its roots to Marxist theories that saw crime as ultimately a product of conflict between different classes under the system of capitalism. Criminology conflict theory suggests that the laws of society emerge out of conflict rather than out of consensus. It holds that laws are made by the group that is in power, to control those who are not in power. Conflict theorists propose, as do other theorists, that those who commit crimes are not fundamentally different from the rest of the population. They call the idea that society may be clearly divided into criminals and noncriminals a dualistic fallacy, or a misguided notion. These theorists maintain, instead, that the determination of whether someone is a criminal or not often depends on the way society reacts to those who deviate from accepted norms. Many conflict theorists and others argue that minorities and poor people are more quickly labeled as criminals than are members of the majority and wealthy individuals.

Critical criminology, also called radical criminology, shares with conflict criminology a debt to Marxism. It came into prominence in the early 1970s and attempted to explain contemporary social upheavals. Critical criminology relies on economic explanations of behavior and argues that economic and social inequalities cause criminal behavior. It focuses less on the study of individual criminals, and advances the belief that existing crime cannot be eliminated within the capitalist system. It also asserts, like the conflict school, that law has an inherent bias in favor of the upper or ruling class, and that the state and its legal system exist to advance the interests of the ruling class. Critical criminologists argue that corporate, political, and environmental crime are underreported and inadequately addressed in the current criminal justice system.

Feminist criminology emphasizes the subordinate position of women in society. According to feminist criminologists, women remain in a position of inferiority that has not been fully rectified by changes in the law during the late twentieth century. Feminist criminology also explores the ways in which women's criminal behavior is related to their objectification as commodities in the sex industry.

Others using the social-structural approach have studied Gangs, juvenile delinquency, and the relationship between family structure and criminal behavior.

Social-Process Criminology Social-process criminology theories attempt to explain how people become criminals. These theories developed through recognition of the fact that not all people who are exposed to the same social-structural conditions become criminals. They focus on criminal behavior as learned behavior.

Edwin H. Sutherland (1883–1950), a U.S. sociologist and criminologist who first presented his ideas in the 1920s and 1930s, advanced the theory of differential association to explain criminal behavior. He emphasized that criminal behavior is learned in interaction with others, usually in small groups, and that criminals learn to favor criminal behavior over noncriminal behavior through association with both forms of behavior in different degrees. As Sutherland wrote, "When persons become criminal, they do so because of contacts with criminal patterns and also because of isolation from anticriminal patterns." Although his

theory has been greatly influential, Sutherland himself admitted that it did not satisfactorily explain all criminal behavior. Later theorists have modified his approach in an attempt to correct its shortcomings.

Control theory, developed in the 1960s and 1970s, attempts to explain ways to train people to engage in law-abiding behavior. Although there are different approaches within control theory, they share the view that humans require nurturing in order to develop attachments or bonds to people and that personal bonds are key in producing internal controls such as conscience and guilt and external controls such as shame. According to this view, crime is the result of insufficient attachment and commitment to others.

Walter C. Reckless developed one version of control theory, called containment. He argued that a combination of internal psychological containments and external social containments prevents people from deviating from social norms. In simple communities, social pressure to conform to community standards, usually enforced by social ostracism, was sufficient to control behavior. As societies became more complex, internal containments played a more crucial role in determining whether people behaved according to public laws. Furthermore, containment theorists have found that internal containments require a positive self-image. All too often, a sense of alienation from society and its norms forms in modern individuals, who, as a result, do not develop internal containment mechanisms.

The sociologist Travis Hirschi has developed his own control theory that attempts to explain conforming, or lawful, rather than deviant, or unlawful, behavior. He stresses the importance of the individual's bond to society in determining conforming behavior. His research has found that socioeconomic class has little to do with determining delinquent behavior, and that young people who are not very attached to their parents or to school are more likely to be delinquent than those who are strongly attached. He also found that youths who have a strongly positive view of their own accomplishments are more likely to view society's laws as valid constraints on their behavior.

Political Criminology

Political criminology is similar to the other camps in this area. It involves study into the forces that determine how, why, and with what consequences societies chose to address criminals and crime in general. Those who are involved with political criminology focus on the causes of crime, the nature of crime, the social and political meanings that attach to crime, and crime-control policies, including the study of the bases upon which crime and punishment is committed and the choices made by the principals in criminal justice.

Although the theories of political criminology and conflict criminology overlap to some extent, political criminologists deny that the terms are interchangeable. The primary focus points in the new movement of political criminology similarly overlap with other theories, including the concerns and ramifications of street crime and the distribution of power in crime-control strategies. This movement has largely been a loose, academic effort.

Other Issues

Criminologists also study a host of other issues related to crime and the law. These include studies of the Victims of Crime, focusing upon their relations to the criminal, and their role as potential causal agents in crime; juvenile delinquency and its correction; and the media and their relation to crime, including the influence of Pornography. Much research related to criminology has focused on the biological basis of criminal behavior. In fact, a field of study called biocriminology, which attempts to explore the biological basis of criminal behavior, has emerged. Research in this area has focused on chromosomal abnormalities, hormonal and brain chemical imbalances, diet, neurological conditions, drugs, and alcohol as variables that contribute to criminal behavior.

The true effect of criminology upon practices in the criminal justice system is still subject to question. Although a number of commentators have noted that studies in criminology have led to significant changes among criminal laws in the various states, other critics have suggested that studies in criminology have not directly led to a reduction of crime.

In McCleskey v. Kemp, 481 U.S. 279, 107 S. Ct. 1756, 95 L. Ed. 2d 262 (1987), an individual who had been sentenced to death for a murder in Georgia demonstrated to the U.S. Supreme Court that a criminologist's study showed that the race of individuals in that state impacted whether the defendant was sentenced to life or to death. The study demonstrated that a black defendant who had killed a white victim was four times more likely to be sentenced to death than was a defendant who had killed a black victim. The defendant claimed that the study demonstrated that the state of Georgia had violated his rights under the EQUAL PROTECTION CLAUSE of the Fourteenth Amendment, as well as under the Eighth Amendment's protection against Cruel and Unusual Punishment.

The high court disagreed. Although the majority did question the validity of the study's findings, it held that the study did not establish that officials in Georgia had acted with discriminatory purpose, and that it did not establish that racial bias had affected the officials' decisions with respect to the death sentence. Accordingly, the death sentence violated neither the Fourteenth Amendment nor the Eighth Amendment.

Criminology has had more of an effect when states and the federal government consider new criminal laws and sentencing provisions. Criminologists' theories are also often debated in the context of the death penalty and crime control acts among legislators and policymakers. In this light, criminology is perhaps not at the forefront of the development of the criminal justice system, but it most certainly works in the background in the determination of criminal justice policies.