The Significance of Mental Illness
The Significance of Mental Illness
The Significance of Mental Illness
Capacity in relation to Crime in Hong Kong
6 October, 2022
8 min read


Mental illness and crime are arguably perceived to have close or even causal relation, partly because of the overrepresentation of offenders with mental issues in the criminal justice system. In view of this, under the influence of bias and prejudice, some people may unfortunately hold a hostile attitude towards people with mental illness and consider them as potential threats in society. The situation is apparent when it comes to diseases that the public are unfamiliar with, such as schizophrenia, bipolar disorder and borderline personality disorder, to name a few. Nonetheless, whether there is a relation between crime and mental illness is still in doubt.

This essay looks at the relationship between mental illness and crime, also the defence available for mentally ill offenders, loopholes and the influence of social stigma will be discussed as well.

The relationship between mental illness and crime

For decades, researchers have held diverse opinions regarding the connection between mental disability and crime. The followings will explore their relationship predominantly based on the representative research conducted in Siu Lam Psychiatric Centre (the “Centre”), the only facility that accommodates mentally ill offenders in Hong Kong :

Common Principal Psychiatric Diagnoses

The most common psychiatric diagnosis was “schizophrenia, schizotypal, delusional, and other non-mood psychotic disorders”, which accounts for 25% of the mentally ill perpetrators in the Centre, followed by “mental and behavioural disorders due to psychoactive substance use” (20%). For substance use disorders, a higher percentage is found among males (22%) than females (16%), the discrepancy is more significant for alcohol-related disorders.

The research also points out that 25% of males and 33% of females in custody are diagnosed with two or more mental illnesses.

The Crime

On the understanding that the crime rate in Hong Kong is relatively low and extremely serious crime rarely happens, the most prevalent offences that the mental patients were found guilty of are theft (22%) and acts intended to cause injury (20%).

For shoplifting cases, it has a higher association with middle-aged women with anxiety and depression symptoms. Some shoplifters are known as “thrill-seekers” as they enjoy the thrill brought by shoplifting; hence, there is a pattern that these shoplifters tend to steal inexpensive merchandise . The research also indicates that offences involving violence were more common in males than in females.

Assaultive violence is also found to have close association with psychiatric illnesses in foreign countries such as the US. Foreign academic even proposed the “deviance hypothesis” , suggesting that mentally ill perpetrators tend to commit more deviant crimes, such as sexual offences and homicide.

The Linkage

Direct causal link between psychiatric illness and criminality has not been proven at this stage yet, however, statistics shows that offenders with mental illnesses tend to have more frequent appearances in the criminal justice system than offenders without .

In addition, symptoms of certain psychiatric illnesses do stimulate a person to aggression or violence, raising their tendency to commit a crime more than a reasonable person .

The Insanity Defence in Hong Kong

To find a suspect to be guilty of a criminal charge, two elements have to be proven: Actus Reus (guilty act) and Mens Rea (guilty mind). For offenders that have unsound mental conditions at the material time of the incident, they may plead the insanity defence.

The M’Naghten Rule

In Hong Kong, the insanity defence is based on the M’Naghten Rule , also the first rule that is commonly adopted here. The questions in concern are:

  1. whether the defendant knows what he was doing when the crime was committed; and

  2. whether the defendant understands that the action he committed was wrong.

If the answers are “no”, it would be a valid insanity defence. In other words, if the offender did not perceive that he was committing a wrongful or criminal act as a result of mental illness, the mental element is absent, hence it is inappropriate to find him guilty.

Section 74 of the Criminal Procedure Ordinance states that if a person was insane at the time of the crime, the jury shall return a special verdict that the accused person is not guilty by reason of insanity. Therefore, the person being convicted under the M’Naghten rule would be sent to psychiatric institutions for treatment, he may spend years or even the rest of his life there depending on the case .

The Durham Rule

Despite not being commonly used in Hong Kong, the Durham rule is another rule that the insanity defence is based upon. For the Durham rule, the focus is on the causation of the crime, it states that a criminal defendant is not criminally responsible if his unlawful act was the result of a mental disease or defect.

Emphasis is placed on the psychological evaluations and testimony under this rule, once evidence indicates that the defendant is subject to a mental illness, a defence of insanity is likely to succeed.


The insanity defence could be abused under different circumstances. The Durham rule might generate a loophole for unlawful and biased psychological testimony . As the rule only concerns causation of the crime, once a psychologist can testify that the criminal offender was mentally ill, the offender would be acquitted. Thus, there is a possibility that some psychologists would create new mental diseases to help their clients get rid of the charges, which would go against the maxim Fiat Justitia.

Stigmatisation and Discrimination

In the Courtroom (Judge and Jury)

For judges, they may subconsciously relate mentally ill offenders to poor attitudes that could be seen in the courtroom. In a Hong Kong case where a schoolteacher was found guilty of assault at a Magistrates’ Court, the Magistrate doubted whether the offender was associated with mental illnesses, simply based on his attitudes of showing no remorse and continuously telling lies . Notwithstanding the fact that individuals suffering from mental illnesses are one of the stigmatised groups in the society, the word of the Magistrate implied that he identified disrespectful attitude as a common feature of mentally ill offenders. Additionally, words carrying negative meanings like “insane” and “lunatic” are still frequently in use in courtrooms to describe these offenders.

Since the jury hear and pass verdict on an accused person in a criminal case, there is a concern that the social stigma associated with mentally ill person might affect their judgement. Despite having a foreign context, the research conducted by Mossiere and Maeder (2016) indicates that the influence of a criminal defendant on the jury verdicts is mild . However, the participants (jurors) tend to pass a guilty verdict to a defendant with substance abuse disorder and a verdict of NCRMD (Not Criminally Responsible on Account of Mental Disorder) to those suffering from schizophrenia, depression and bipolar disorder. The principal reason is the result of the perception that offenders with substance abuse should have a higher ability of control over their behaviour and to act logically.


In the era with unprecedented technological advancement, people see the world through media. Arguably, one’s perception of the world is majorly influenced by the information one obtains . When the media has such a great power in shaping perspectives towards different issues, and they choose to associate mental illnesses with dangerousness and criminality, it is not difficult to understand why the public may hold prejudicial attitudes toward the mentally ill group .

Stigma usually stems from the lack of understanding or fear, it is important to note that only a small group of mentally ill patients are criminal offenders. Despite this group of people may have a higher tendency to commit crime under the influence of various symptoms, it does not justify any form of discrimination.


Although a certain degree of connection between one’s psychiatric health and his tendency to commit a crime could be found, it is unjust to conclude that mentally ill individuals should be tied with the word “criminals”. The stigma and prejudice held against them are part of the reasons why they could be reluctant to seek help.

Furthermore, by looking into the pattern of crime committed by offenders with different mental issues respectively (i.e. patients with depression and anxiety have a higher tendency to commit shoplifting), the authorities can offer relevant assistance to this vulnerable group and to control the crime rate.

It might be difficult to strike a balance between protecting the interests of the mentally ill offenders and having a stricter law to prevent abusive acts, but work needs to be done to address gaps and ensure psychiatric care can reach the people in need.