This article from the Online Dictionary of Social Sciences, provides a brief introduction to the idea of labeling theory. The above link will lead the reader to this article on the web, where links to related articles can be found.

A theory which arose from the study of deviance in the late 1950’s and early 1960’s and was a rejection of consensus theory or structural functionalism. These approaches to deviance assumed that deviance could be understood as consisting of behaviour that violates social norms. Deviance is therefore something objective: it is a particular form of behaviour. Labeling theory rejected this approach and claimed that deviance is not a way of behaving, but is a name put on something: a label. Law is culturally and historically variable: what is crime today is not necessarily crime yesterday or tomorrow. For example in 1890 it was legal to possess marijuana, but illegal to attempt suicide. Today, the law is reversed. This shows that deviance is not something inherent in the behaviour, but is an outcome of how individuals or their behaviour are labeled. If deviance is therefore just a label it makes sense to ask: where does the label come from? How does the label come to be applied to specific behaviours and to particular individuals? The first question leads to a study of the social origins of law. The second question leads to an examination of the actions of labelers such as, psychiatrists, police, coroners, probation officers, judges and juries.