Research has found that a variety of factors can indicate or influence who commits a crime, including gender, age, relationships and mental health.

Gender

In the Western world, 90% of murders are committed by males.  Males are also the victims in 75% of murders.
In terms of police prosecutions, about three quarters of proceedings annually are against males. The most common offence for both males and females is acts intended to cause injury which accounts for about a quarter of both the male offender group and female offender group. 

Age

Age also affects murder rates, there is an increase in murders between the ages of 17 and 30.  People are less likely to commit murder as they age, but murders committed by children and adolescents are also rare.  However, if we look at research across different countries and cultures, the patterns do not always appear similar. For example, in Korea, according to the Asian Correspondent newspaper, 37.4% of murderers are men, which is obviously less than in America. But all the criminals had committed their crimes in their 30s.

With regards to crimes, the peak age for committing crimes is the teenage years. In many societies, rate of offending rises sharply from late childhood peaking at around 18 years, slowly declining to age 40 years, and then tailing off quickly into late adulthood. However, the proportion of young offenders is significantly less than adult offenders. Also, while adolescents are more likely to commit crimes against the person, the seriousness of their offences is less than for adults. 

Relationships 

We often watch movies and TV programmes where we think it is going to be the spouse who did the murder.  But the Crime Prevention Research Centre in America found that –

• 9.4% of murders were committed by a husband, wife, common-law husband or wife, father, mother, son, daughter, brother, sister-in-law, stepfather, stepmother, stepson, or stepdaughter.
• 1.8% were other family members.  
• 4.2% were boyfriends, girlfriends, ex-husbands, or ex-wives.
• 14% were acquaintances. This is a broad category can include taxi drivers to prostitutes and their customers.
• 3.1% were a friend.
• 5.4% were other known.
• 11% a stranger.
• 39% was an unknown relationship. For example, they participated in a gang fight but there was no apparent direct relationship between the victim and murderer.
• 1% a neighbour.

But even looking at these statistics, it is not so clear cut. With family murders, the murderers tended to also have a criminal record for other crimes, so it is not just a simple someone in the family murdered the person.

Mental Illness 

There is often a misconception that people who commit murder are mentally ill.  However, this is not always the case.  The Asian Correspondent reported that 81.3% of Korean murderers had no specific mental illness. 3.9% suffered depression, 0.7% had a mental illness.  Time to Change in the UK reports that most murders are committed by people who do not have mental health problems.  They estimate that there are 50 – 70 murders per year that involve a person with a mental health problem at the time of the murder.  

It also depends on the type of mental illness being discussed. Some research has found that people with some mental health conditions are more prone to commit some types of crimes, e.g., violent crimes, than other types of crime. However, much of this research has been conducted on prison populations and psychiatric patients. Some conflicting studies involving people with mental health conditions in the community have revealed no statistical difference in crime rates to the general population, and that people with mental health conditions are not associated with specific types of crime. Regardless, of those with mental health conditions associated with crimes, some of those conditions are outlined:

• Antisocial personality disorder – a personality disorder that usually begins in childhood or the early teens. There is a lack of remorse and a disregard for punishment.
• Narcissist – The person will be fascinated with themselves. They will be vain and have excessive self-love.  The “God Complex”, which can be found in rapists and serial killers.
• Psychopath – A person with a chronic mental disorder. They will have violent or abnormal social behaviour.
• Schizoid – A personality disorder where the person is dissociated, passive, withdrawn, indifferent to praise and criticism and unable to form warm social relationships.
• Schizophrenia – Schizophrenia is a severe mental disorder, which leads to intellectual deterioration, negative affect (a lack of observable emotion), social isolation, disorganized speech, delusions, hallucinations. Whilst we are mentioning this here, research does suggest that the link between schizophrenia and crime is low.  Research by Walsh et al found that there is a higher level of violence found in people with schizophrenia. BUT the level is still very small, less than 10% of violence. They found that “Most studies confirm the association between violence and schizophrenia. Recent good evidence supports a small but independent association. Comorbid substance abuse considerably increases this risk. The proportion of violent crime in society attributable to schizophrenia consistently falls below 10%. This does show that additional substance abuse increases the risk substantially, so support with drug misuse could help reduce this.
• Sociopath – A person with a psychopathic personality. Their behaviour is antisocial. They lack moral responsibility or a social conscience. This trait is often seen in serial killers.

Two other important terms when considering mental health issues – 

• Delusion – a delusion is a false belief or opinion.  The person may believe that the belief is a real fact. For example, the person may believe that they can control others with their mind. Or they may have delusional jealousy, believing that their partner is having an affair.
• Hallucination – a sensory experience of something that does not exist outside the mind. It can be caused by physical or mental disorders. Hallucinations are usually auditory or visual. For example, a person may hear voices.

How to minimise Crime

Crime prevention starts with understanding criminal psychology, and the nature of people who are more likely to commit crime.  Anyone who works in crime management should have this sort of knowledge - not only law enforcement officers, but many other professions too, from security guards and prison officers to social workers and parole officers.

Relate Courses include: Criminal Psychology, Security Management, Forensic Science and Criminal Profiling.