7. Psychological Theories of Crime

7.4 Medical Model of Psychopathology and Criminal Behaviour

Dr. Jennifer Mervyn and Stacy Ashton, M.A.

Although mental illness would seem to fall solidly in the camp of individual psychology, the interface between mental illness and criminality is as much socially determined as it is individually determined.

Theories that draw a straight line between individual mental illness and criminal behaviour rely on the medical model of mental illness, with its focus on abnormal psychology. In the early 1900s, doctors and psychiatrists began seeking ways to classify recurring patterns of thought and behaviour that significantly reduce an individual’s ability to function in an attempt to diagnose and treat “mental illness” utilising an approach similar to that used to deal with physical disease.

Today, the Diagnostic and Statistical Manual of Mental Disorders (DSM–5; American Psychiatric Association, 2013) is used in North America to diagnose mental disorders. The DSM-5 describes mental disorders, their symptoms, and the criteria for diagnosing them. The DSM-5 seeks to ensure clinicians are consistent in their communication about disorders and diagnostic criteria and researchers are consistent in how they define disorders so that they can meaningfully add to the body of scientific knowledge. As most research that informs the DSM has involved predominantly white Americans, it is acknowledged that there is limited evidence of the cross-cultural validity of the DSM. To the extent that mental illness leads to behaviours that violate the norms and standards of a particular society, people with mental illness would be expected to have a higher rate of contact with the criminal justice system.

Indeed, in Canada as elsewhere, people with mental illness are over-represented in the criminal justice system. In 2011–2012, 36% of federal offenders were identified at admission as requiring psychiatric or psychological follow-up, while 45% of male inmates and 69% of female inmates received institutional mental health care services (Sapers & Zinger, 2012). Olley et al. (2009) found up to three times higher rates of mental illness in incarcerated populations.

The over-representation of people with mental illness in the corrections system appears to be increasing over time. Between 1997 and 2010, symptoms of serious mental illness reported by federal offenders at admission increased by 61% for males and 71% for females (Sorenson, 2010). During this time frame, psychiatric institutions were being shut down in favour of community-based mental health care. Unfortunately, community mental health did not receive adequate funding, leading individuals with disruptive symptoms and untreated mental illness to come to the attention of police. Sapers (CTV News, 2010) stated that the mentally ill are being ‘warehoused’ in federal prisons instead of receiving the health care they need; prisons simply do not have the capacity to meet the complex mental health needs of inmates.

When mental illness and addiction are treated as health issues instead of criminal justice issues, we see hopeful results (Hammond, 2007). In Canada, collaborative partnerships between the criminal justice system and healthcare system are associated with better outcomes for youth. Cuellar et al. (2006) found that offending youth with mental illness who accessed diversion programs that offered treatment fared better than those who faced punishment. Lamberti (2016) also advocates for mental health collaboration with the criminal justice system so that treatment, not punishment, is the focus.

Although social factors such as underfunded mental health systems, poverty, and a lack of access to treatment play a part in the over-representation of people with mental illness in the criminal justice system, some mental illnesses include criminal behaviour as part of their diagnostic criteria, including antisocial personality disorder, psychopathy, psychosis, and substance abuse disorders.

Antisocial personality disorder

(ASPD) is one of a class of diagnoses that describe persistent, longstanding, maladaptive ways of thinking and feeling about oneself and others that detrimentally affect how one functions. ASPD is the personality disorder most strongly linked with violence; it is defined by a continual remorseless disregard for the rights of others, including repeated criminal acts, impulsiveness, irresponsibility, deceptiveness, and aggression. To be diagnosed with this disorder, the person must have exhibited aspects of antisocial behaviour prior to age 15, such as aggression toward people or animals, theft, or property destruction (American Psychiatric Association, 2013). Only adults over the age of 18 can be diagnosed with personality disorders under DSM-5 criteria; however, personality disorders are commonly attached to youth in order to secure treatment.


Although is not recognised in the DSM-5, it is associated with, but distinct from, conceptualisations of ASPD. Psychopathy is characterised by two main factors: 1) interpersonal and emotional traits, such as manipulation, grandiosity and impaired empathy, and 2) antisocial behaviour and lifestyle traits, such as impulsive behaviour, sensation seeking and a parasitic lifestyle. Psychopathy is defined by subjective emotional and interpersonal criteria that are not part of ASPD, and because the DSM emphasises observable, objective behavioural criteria, not part of the DSM. The Psychopathy Checklist – Revised, developed by Hare (1991) is the most commonly used measure for psychopathy (Hare, 2016).

The twenty traits assessed by the PCL-R score are:

  • glib and superficial charm
  • grandiose (exaggeratedly high) estimation of self
  • need for stimulation
  • pathological lying
  • cunning and manipulativeness
  • lack of remorse or guilt
  • shallow affect (superficial emotional responsiveness)
  • callousness and lack of empathy
  • parasitic lifestyle
  • poor behavioural controls
  • sexual promiscuity
  • early behaviour problems
  • lack of realistic long-term goals
  • impulsivity
  • irresponsibility
  • failure to accept responsibility for own actions
  • many short-term marital relationships
  • juvenile delinquency
  • revocation of conditional release
  • criminal versatility (Hare, 2016).

Research generally indicates that psychopathy, particularly the theorised sub-type called primary psychopathy, involves brain-based differences that impact emotional and cognitive functioning (Blair et al., 2008; Kiehl, 2006; Koenigs, 2012; Patrick, 2018; Yang & Raine, 2009). Two models are the current top explanations for this impaired emotional functioning (Smith & Lilienfeld, 2015): 1) the low fear model, which states that emotional deficits result from an impaired recognition/experience of fear (Lykken, 1957, 1995), leading to increased sensation seeking and an inability to be deterred by fear of punishment and 2) the response modulation hypothesis, which describes an individual’s impaired ability to modify their behaviour once they have focused their attention, even though the situation might warrant a behaviour change (Newman et al., 1987).

Psychopathy is associated with high reoffending rates (Shepherd et al., 2018; Thomson et al., 2018) and treatment resistance (Olver et al., 2011). For these reasons, psychopathy has been an important consideration for decision-making in the justice system, with a diagnosis of psychopathy leading to dangerous offender classifications and indefinite sentencing. In recent years, though, there have been concerns about how psychopathy has been defined and utilised in the justice system (Skeem et al., 2011), leading to alternative conceptualisations of psychopathy (Lilienfeld & Widows, 2005). What is Psychopathy addresses what psychopathy is and differentiates between psychopathy and ASPD, as evidenced in the research.

How psychopathy has been defined and utilised in the justice system, and the reliance on psychopathy scores in risk assessment instruments, is particularly relevant and concerning when examining their use with Indigenous offenders. As Hassan (2010) demonstrates in her analysis of psychiatric assessments administered on Indigenous versus non-Indigenous long-term offenders (LTOs) in British Columbia in the first 10 years of the use of this designation in Canada, twice as many LTOs categorised in the high psychopathic range were Indigenous compared to their non-Indigenous counterparts (46% vs 23%, respectively). Moreover, while the percentage of LTOs categorised in the intermediate category was approximately the same in these two groups (46% of the Indigenous LTOs vs 43% of LTOs not identified as Indigenous), only one (9%) of the Indigenous LTOs assessed using the PCL-R was categorised in the non-psychopathic range, as compared to 10 (33%) of the LTOs not identified as Indigenous. Hassan (2010) also found that amongst those LTOs whose files were included in her analysis, a disproportionately high number of Indigenous LTOs were deemed untreatable compared to their non-Indigenous counterparts.

The clear overrepresentation of Indigenous LTOs in the high psychopathic range and in the untreatable category calls into question the objectivity and neutrality of the tests used to assess this population. The reduction of human behaviour to a quantifiable score results in an undeniable loss of personal information and blatantly disregards the impacts of colonisation and genocide experienced by Indigenous populations across Canada and beyond.


Psychosis is a condition that impacts how your brain processes information and is present in some severe mental illnesses, including schizophrenia and mood disorders such as depression and bipolar disorder. The vast majority of individuals experiencing breaks from the shared reality of the general population do not engage in aggressive or criminal behaviour; in fact, people with mental disorders are more likely to be victims of violence than perpetrators (Elbogen & Johnson, 2009). Psychosis can generate specific hallucinations, such as hearing voices or seeing things that do not exist, and delusions, where a person experiences strongly held but false beliefs that may include paranoid ideas about being persecuted (American Psychiatric Association, 2013). In rare cases, the nature of the hallucination or delusion can lead to inappropriate “self-defence” or other criminal behaviour that would be understandable in light of the beliefs held during a psychotic break (Chan & Shehtman, 2019; McNiel et al., 2000).
The Canadian justice system requires that individuals can only be punished for their crimes when they have mens rea: they must know what they are doing and know that it is wrong (see 1.2 Crime in Canada). People who have mental disorders, particularly while in psychotic states, may lack this awareness and therefore be found Not Criminally Responsible on Account of Mental Disorder (NCRMD), as defined in Section 16 of the Criminal Code of Canada (RSC 1985, c C-46). Importantly, if someone knew an action was against the law but believed they were morally doing the right thing, the NCRMD defence can still apply (R v Chaulk, 1990).

Although some psychosis can lead to violent behaviour, far more often, people with active mental illnesses are charged with minor offenses that begin a long cycle of involvement with criminal justice systems. A major depressive episode with catatonic features in a homeless person looks very much like loitering in the eyes of police. One study found that 40% of police encounters with people with mental illness involve non-violent crime, and another 40% involve non-criminal mental health crises, bizarre behaviours, and/or criminal victimisations. Only two in 10 police interactions with people with mental illness involved any type of violent crime (Brink et al., 2011).

Substance Abuse Disorders

are characterised by difficulties reducing substance use, causing problems in one’s personal and work life (American Psychiatric Association, 2013). Because many substances are in themselves illegal to possess and use, the defining behaviour of substance abuse is criminalised if the addictive substance is restricted.

Aside from the inherent criminal behaviour of using a prohibited substance, the tripartite conceptual model (Goldstein, 1985) outlines three main ways that substance use is connected to violent criminal behaviour (see Table 7.8).

Table 7.8: Tripartite Conceptual Model of the Drug/Violence Nexus
(Goldstein, 1985)
Systemic crime Crime related to the drug trade, including selling drugs and the violence associated with that.
Economically compulsive crimes Result from people engaging in money-making crime to support their substance use.
Psychopharmacologically-driven crime The substance itself produces an effect on the brain and behaviour, resulting in crime or violence.

Legal codes that criminalise addiction set the stage for systemic and economically compulsive crimes. If access to drugs that people are addicted to is against the law, unlawful organisations that provide drugs to people with addictions become highly profitable and are maintained through violence if necessary. If people addicted to drugs are less likely to have the ability to support themselves through legal means, they will be more likely to commit crimes to meet their needs. Countries such as Portugal have been decriminalising drugs in favour of on-demand treatment, resulting in reductions in drug use and related crimes. See How Portugal Won Its War On Drugs for a summary of Portugal’s approach.


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Introduction to Criminology Copyright © 2023 by Dr. Jennifer Mervyn and Stacy Ashton, M.A. is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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