Defining Criminal Behaviour in Forensic Psychology

What exactly makes an act “criminal”? It might seem obvious-someone breaks the law, and that’s a crime. But in forensic psychology, the answer is far more layered. Criminal behaviour is not simply about violating a statute. It involves intent, motivation, learning, and a web of hereditary and environmental influences that forensic psychologists spend their careers trying to untangle. Understanding how criminal behaviour is defined is the foundation of forensic psychological assessment, and it shapes how we investigate, judge, and rehabilitate offenders.

What is criminal behaviour? 🔗

At its core, criminal behaviour refers to intentional actions that violate established laws and societal norms, resulting in harm or the potential for harm to individuals, property, or the broader community. But this definition carries more weight than it first appears. Not every harmful act is criminal. Smoking, for instance, harms the individual, but it is not a crime. Breaching a contract is a civil wrong, not a criminal offence. What sets criminal behaviour apart is that the state-through its legal apparatus-has specifically designated certain harmful acts as punishable offences.

This distinction matters in forensic psychology because it determines who enters the criminal justice system and who does not. Forensic psychologists do not just study what people do; they study why people do it, the psychological states behind the act, and whether the behaviour meets the legal threshold for criminal responsibility.

Tappan’s definition: intent as the cornerstone 🔗

One of the most widely cited definitions of crime comes from Paul Tappan, a criminologist and legal scholar. In 1947, Tappan defined crime as an intentional act committed in violation of the criminal law, carried out without legally acceptable defence or excuse, and penalised by the state. This definition remains a cornerstone of criminological and forensic psychological thinking.

The critical word here is intentional. Tappan’s framework draws a clear line between deliberate criminal acts and accidental harm. If a driver loses control of their vehicle due to a sudden medical emergency and injures a pedestrian, Tappan’s definition would not classify this as criminal behaviour-there was no intent to cause harm. On the other hand, if a driver deliberately runs a red light at high speed, knowing the risk to others, that intentionality transforms the act into a potential crime.

This focus on intent is crucial in forensic psychological assessment. When psychologists evaluate a defendant, they assess not only what happened but what the person intended and understood at the time. Did the accused know what they were doing? Did they appreciate that their actions were wrong? Were they acting under duress or compulsion? These questions directly stem from Tappan’s emphasis on intentionality as the defining feature of criminal behaviour.

Distinguishing crime from accident and duress 🔗

Tappan’s definition also explicitly excludes acts committed with a legally acceptable defence. This includes actions taken under duress-where someone is forced by threat or coercion to commit an act they would not otherwise perform. It also accounts for situations involving self-defence, necessity, or insanity.

For forensic psychologists, this is where much of the real work begins. A significant part of forensic psychological assessment involves determining whether a defendant had the mental capacity to form criminal intent, or whether psychological conditions such as severe mental illness, intellectual disability, or extreme emotional disturbance compromised that capacity. The legal system, guided by Tappan’s principles, does not treat all law-violating acts the same. Context and mental state matter.

Criminal behaviour as learned behaviour 🔗

One of the most important insights in understanding criminal behaviour is that it is largely learned. This idea was most thoroughly developed by Edwin Sutherland through his differential association theory, first proposed in 1939. Sutherland argued that criminal behaviour is learned through interaction with others-just like any other type of behaviour. People do not simply decide to commit crimes in isolation. They pick up criminal attitudes, techniques, and rationalisations from their social environment, particularly from close personal groups like family, friends, and peers.

Sutherland identified several key principles. Criminal behaviour involves learning the actual techniques of committing crimes, as well as the motives, drives, and rationalisations that support those crimes. A person becomes criminal when the definitions they have absorbed that are favourable to breaking the law outweigh the definitions unfavourable to it. In other words, if someone is surrounded by people who normalise theft, justify violence, or reward illegal activity, they are far more likely to adopt those behaviours themselves.

Social learning theory and reinforcement 🔗

Albert Bandura’s social learning theory expanded on this idea by demonstrating that people learn not only through direct experience but through observation and imitation. His famous Bobo doll experiments showed that children who witnessed aggressive behaviour were more likely to reproduce it-even without direct reinforcement. In the context of criminal behaviour, this means a young person who repeatedly observes violence or criminal acts in their household or neighbourhood can internalise those behaviours as normal responses to conflict or adversity.

Ronald Akers later integrated Sutherland’s and Bandura’s work into a criminological framework known as social learning theory. Akers added the concept of differential reinforcement-the idea that behaviours are strengthened or weakened depending on the rewards and punishments they produce. If someone commits a robbery and is rewarded with money, status, or peer approval, and faces no immediate negative consequences, the behaviour is reinforced and more likely to be repeated.

This perspective has major implications for forensic psychology. It suggests that criminal behaviour is not simply a character flaw or moral failing-it is a pattern of behaviour that has been shaped, reinforced, and sustained by an individual’s social environment. This understanding guides rehabilitation efforts, which focus on restructuring the social learning processes that led to criminal behaviour in the first place.

The role of hereditary and biological factors 🔗

While learning and environment are powerful shapers of criminal behaviour, they do not tell the whole story. Research in behavioural genetics and neuroscience has shown that hereditary and biological factors also play a significant role. This does not mean there is a “crime gene.” Rather, certain genetic predispositions-toward impulsivity, sensation-seeking, low empathy, or aggression-can increase an individual’s vulnerability to criminal behaviour when combined with environmental risk factors.

Meta-analyses have estimated that the heritability of antisocial behaviour is approximately 40-60%, meaning that a substantial proportion of the variation in such behaviour across a population can be attributed to genetic differences. Shared environmental factors account for roughly 11-14% of the variance, and non-shared environmental factors explain about 31-37%.

One particularly well-researched example involves the monoamine oxidase A (MAOA) gene. Studies have found that individuals with a low-activity variant of the MAOA gene who were also exposed to childhood maltreatment were significantly more likely to develop antisocial behaviour than those with the high-activity variant. This is a textbook case of a gene-environment interaction-neither the gene nor the environment alone determines the outcome, but their combination dramatically increases risk.

Psychophysiological factors 🔗

Beyond genetics, psychophysiological characteristics have also been linked to criminal behaviour. Research has consistently found that individuals with low resting heart rate are more likely to engage in antisocial and criminal acts. Two theories explain this. The fearlessness hypothesis suggests that these individuals do not experience the same physiological arousal in response to danger or risk, making them less deterred by potential consequences. The sensation-seeking hypothesis proposes that low arousal is an uncomfortable state, and individuals engage in risky or criminal behaviour to raise their arousal to a more comfortable level.

These biological findings do not excuse criminal behaviour. They do, however, add depth to our understanding. In forensic psychology, recognising the biological dimension helps professionals develop more targeted interventions-particularly for individuals whose criminal behaviour may be rooted in neurobiological vulnerabilities rather than purely social influences.

Criminal behaviour as subjectively adaptive 🔗

Here is a concept that often surprises people: criminal behaviour can be subjectively adaptive. This means that from the offender’s perspective, the criminal act may serve a perceived purpose or solve a perceived problem. A person who steals to feed their family sees the theft as a rational solution to an immediate crisis. Someone who commits assault in response to a perceived insult may view the act as necessary to maintain social standing within their community.

This does not make the behaviour morally acceptable or legal. It does, however, reveal something important about the psychology behind criminal acts. Forensic psychologists recognise that criminal behaviour is often the product of an individual’s unique problem-solving strategies-strategies shaped by their life experiences, cognitive patterns, and available resources. When legitimate options are absent, perceived as unavailable, or never learned, individuals are more likely to resort to unlawful means.

This perspective is directly influenced by a combination of the hereditary dispositions and environmental conditions discussed earlier. A person with a genetic tendency toward impulsivity, raised in poverty with limited education and exposure to criminal role models, has developed a problem-solving repertoire that heavily favours short-term, high-risk solutions. The criminal act is deviant and harmful to society, yet it is subjectively functional for the individual.

Environmental factors shaping criminal behaviour 🔗

No discussion of criminal behaviour would be complete without acknowledging the environmental forces that contribute to it. Family structure, peer influence, socioeconomic conditions, educational opportunities, and neighbourhood characteristics all play substantial roles.

Children raised in aggressive or chaotic family environments are more susceptible to developing criminal behaviour. Research has consistently shown that factors like parental rejection, inconsistent discipline, poverty, and low educational attainment are significant predictors of later criminal activity. The family environment does not just model behaviour-it shapes the individual’s capacity for self-regulation, empathy, and conflict resolution.

Peer groups become increasingly influential during adolescence. A young person who affiliates with peers who engage in delinquent behaviour is far more likely to become involved in criminal activity themselves. This aligns with both Sutherland’s differential association theory and Akers’s social learning theory-the more intense and frequent a person’s exposure to criminal norms, the more likely they are to internalise them.

Socioeconomic disadvantage adds another layer. While poverty does not cause crime directly, it creates conditions-limited access to education, healthcare, and stable employment-that increase vulnerability. Individuals in disadvantaged settings may have fewer legitimate pathways to achieve social goals, making criminal behaviour appear as a more accessible, though deviant, alternative.

Why defining criminal behaviour matters in forensic psychology 🔗

For forensic psychologists, the definition of criminal behaviour is not an academic exercise-it is a practical necessity. Every forensic assessment, every risk evaluation, and every treatment plan depends on a clear understanding of what criminal behaviour is and what drives it.

If criminal behaviour is purely a matter of choice, then punishment alone should be sufficient to deter it. But as we have seen, criminal behaviour is the result of a complex interplay among intentionality, learning, genetics, biology, and environment. This means that effective responses must go beyond punishment. Rehabilitation programmes informed by social learning theory, cognitive-behavioural interventions addressing distorted thinking patterns, and targeted support for individuals with neurobiological vulnerabilities are all essential components of a comprehensive approach.

Tappan’s legal definition gives us the framework: criminal behaviour is intentional, unlawful, and punishable. But forensic psychology fills in the rest of the picture-the why behind the act-making it possible to not only respond to crime after it occurs but to identify risk factors and intervene before it does.

What do you think? If criminal behaviour is shaped by a combination of genetic predispositions, learned behaviours, and environmental pressures, how should this influence the way we approach punishment and rehabilitation? And where do you draw the line between understanding the causes of criminal behaviour and holding individuals accountable for their actions?

References

1. https://www.psychologytoday.com/us/basics/forensic-psychology
2. https://criminal-justice.iresearchnet.com/criminology/history-of-criminology/
3. https://kpu.pressbooks.pub/introcrim/chapter/9-4-social-learning-theory/
4. https://criminal-justice.iresearchnet.com/criminology-theories/social-learning-theory/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6640871/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC2174903/
7. http://www.personalityresearch.org/papers/jones.html