Thanet Writers Research Causes of Criminality

Writer Seb Reilly researches the causes of criminality on behalf of Thanet Writers.

Image Credit: 
Jakub Schikaneder / Public Domain

Crime features heavily in fiction, not only as part of tales focusing on detectives or transgressive characters, but also amongst many other genres and within stories of all types. The idea of the criminal mind is one that many find fascinating, as it seems so alien to what is widely regarded as ‘normal.’

Unfortunately, a lot of writers rely on the traditional tropes of so-called psychopaths (often using that term incorrectly) or use stereotypical criminals based on the misconceptions of other fiction, rather than researching the facts. For example, criminal acts are committed most frequently during the teens and twenties, and those that occur later in life are considerably less likely.

Whilst there will always be exceptions to rules, it is wise to consider the trends which are visible by evaluating the wealth of statistics available from over a century of police investigations and court convictions, especially taking into account modern policing methods and scientific advances in forensics and psychology.


The likelihood of criminal behaviour later in life can start within the womb. Maternal smoking during pregnancy, for example, or complications during birth both show an increase in potential for criminality, although this should always be considered as an additional influence that must be associated with several other factors.

Child maltreatment and low parent-child attachment (especially where the parent did not want the child), along with family discord or a dysfunctional early home life, plus drug and alcohol abuse within the family, can contribute to criminal probability. Malnutrition—particularly a deficiency in zinc, iron, protein and vitamin B—from infancy shows a dramatic increase in violent and controlling behaviour in later life, along with increased aggression and a lower IQ. Other factors to consider include family size and birth order, bed-wetting, and low levels of parental supervision.

As childhood progresses, bullying, disciplinary problems within school, truancy, low test scores or grade results, and dropping out of school can all be precursors to criminal behaviour, and crime is higher among adults who, as children, experienced some or all of these.

Throughout teenage years and early adulthood, excessive alcohol consumption (including alcohol abuse and alcoholism) and high illegal drug use and dependence can lead rapidly to crime. An early age of first sexual intercourse, plus the number of sexual partners, shows correlation with criminal activity. Social isolation is also a factor, as is social influence from criminal peer groups and gang membership.

Some studies have suggested that growing up within a religious environment can lower the chances of criminal activity, but the data is not conclusive.


Various factors within adult life can lead to crime, along with those already identified in teenage years that can still hold influence, including childhood conduct disorder and adult antisocial personality disorder (which are associated with each other), ADHD, depression, suicidal tendencies and schizophrenia.

Dramatic shifts in belief or lifestyle, including religious conversion or abandoning faith, breakup of relationships, death of family or close friends, and newfound addiction or withdrawal from an existing addiction can all increase the potential for criminality. Political leanings, whether new or ingrained, have been found to correlate with involvement in violence, or not, depending on ideals. Liberal self-classification can, among some groups, be positively associated with non-violent criminal behaviour compared to conservative self-classification.

IQ level does correlate, to some degree, with crime, if levels resulting from learning disabilities are discounted. In this case, IQ is generally negatively associated with crime, with those possessing a higher IQ being less likely to commit criminal activity. Certain personality traits can also be closely associated with criminality, including impulsivity, sensation-seeking, low altruism, low empathy, a lack of self-control, childhood aggression, and psychoticism.

Other than self-reported illegal drug use, socioeconomic status negatively correlates with crime. This is usually measured using three variables: income, occupational level, and years of education. A high frequency of unemployment and unstable employment correlate positively with criminality.

Geographical location and local economy are also relevant to criminal probability. Factors include population, residential and social mobility, alcohol density, gambling and tourism, temperature, weather and seasons, and proximity to the equator. Whilst some multi-racial or ethnically-diverse areas show increased crime levels, in others the statistics are considerably lower than homogeneous places, and so direct correlation between immigration or diversity and crime cannot be drawn.


Males commit more crime than females. Males are considerably ahead, statistically speaking, in terms of committing both violent crime (other than infanticide) and property crime, with the exception of shoplifting, which is roughly an equal split between genders. Females appear less likely to reoffend.

It has been suggested that how both genders behave regarding aggression is affected by beliefs about the negative consequences of violating gender expectations: males are more likely to offer justification of aggression, whilst females offer exculpatory accounts.

Historically, there has been less attention paid to female criminals, often attributed to the view that female crime has almost exclusively been dealt with by men, leading to less theoretical approaches to female crime. Only recently has equality become widely acceptable, so more data and evaluation is now being examined. Violence by females is now being documented more than ever, which is likely the result of a combination of more crime being reported with a disregard for gender, and a potential shift in behaviour as gender equality becomes more widely-accepted and promoted, removing gender-stereotyped inhibitions. That being said, statistically it is still more likely for males to commit violent crime.

Evolutionary psychology proposes several explanations for gender differences in aggression levels, including males increasing their success of reproduction or survival by polygyny, leading to competition with other males. Another area of study is maternal death or abandonment, as maternal investment and nurture is more impactful upon children at a younger age than paternal, and can cause increased aggression in infants during development. On the other hand, higher-than-usual levels of caring for children can result in parents being unable to allow their children to engage their fight or flight response.

The increase of testosterone in males during puberty is closely linked to criminal behaviour; it is evolutionarily designed to facilitate competition and reproduction, thereby also including aggression. Direct correlation has been found in studies between testosterone and dominance (for example, prisoners with the highest testosterone levels are generally the most violent criminals in prison, either by conviction or action), and high levels of testosterone can ‘masculinise’ brains to enhance the ability to obtain resources, in order to survive and reproduce, leading to competitiveness that is at risk of harming others. Researchers have stated this competition is reflected in war, territorial disputes, the acquiring of wealth, and control over others. Additionally, there is a high correlation between criminal acts and males who father children when young.


There are various biological variations between those who do and do not commit criminal acts. Measures of arousal, including skin conductance and heart rate, tend to be lower among criminals. Muscular body-types share a positive correlation with crime, particularly those of a sexual nature.

Aggression has been linked with abnormalities in three of the regulatory systems in the body: serotonin, catecholamine, and the hypothalamic-pituitary-adrenocortical axis. Abnormalities within these systems can also be induced by stress (either severe, acute or chronic low-grade stress).

Genetically, monoamine oxidase A—known as the ‘warrior gene’—is strongly linked to increased tendency towards committing violent crime, as is CDH13, a gene also tied to increased risk of substance abuse. Whilst genetic profiling does not determine criminal behaviour, it does increase its likelihood, particularly when coupled with other factors.

Addictive personality traits are also linked to criminal behaviour, either through cause (an addiction to the chemical reaction to committing crime) or effect (as the addiction becomes motive and inhibitions are lowered).


A criminal is not dictated by general statistics and trends, however the variety of potential contributing factors that increase the likelihood of criminality clearly reflect in case studies. Even the serial killers who have inspired so much fiction will adhere to at least some of these rules. With the huge volumes of data and information available, and over a hundred years of studying criminality, the knowledge available to writers is far greater than it ever has been. Using this detail can enhance characters, plot, backstory, setting, decisions and consequences, and add depth and weight to an often-lazily-written aspect of fiction: the criminal.

Seb Reilly is a writer, fiction author and occasional musician. He lives by the sea in Thanet, Kent, with his family and two cats.

Join the Discussion

Please ensure all comments abide by the Thanet Writers Comments Policy

Add a Comment