Genetics

• Human genes are linked to various behaviors, including crime.Chad Baker/Ryan McVay/Digital Vision/Getty Images
  
  Genetics is most commonly associated with heredity. In mapping the human genome, scientists can determine why people behave the way they do. So far, there has been evidence correlating repeat offenses and property crimes to heredity, while almost no evidence supporting links to violent crimes. However, there is some evidence that, when accompanied with other factors, such as child abuse, certain genotypes can show a predisposition to crime.
  
  

Neurotransmitters

• Low levels of serotonin are associated with heightened levels of aggression.PhotoObjects.net/PhotoObjects.net/Getty Images
  
  Neurotransmitters send information between cells by altering their electrical state or activity. Common examples are Serotonin, Norepinephrine, and Dopamine. Scientists have conducted various studies on Serotonin on excessive aggression and impulse control. As reported by the U.N. Department of Ministry, a strong correlation exists between low levels of serotonin and antisocial behavior among adults as well as children. Another hormone associated with criminal activity in males is testosterone. High levels of testosterone can lead to aggression and anger.
  
  

Neurobiology

• Abnormal brain functioning has been shown in victims of child abuse.Keith Brofsky/Photodisc/Getty Images
  
  Brain damage can be caused by a number of things, from problems during childbirth to a car crash. This damage can result in abnormalities of brain function that can lead to criminal behavior. For example, a 1997 study by Martin Teicher of McClean Hospital, showed child abuse can result in abnormal brain waves as well as abnormal functioning in the left side of the brain, leading to antisocial behavior as children age.
  
  

Socio-Biological

• More than half of the prison population suffer from mental health issues.Thinkstock Images/Comstock/Getty Images
  
  As of 2005, more than half of prison and jail inmates were found to have a mental health problem. The psychological approach to crime mixes biology with other factors known to lead to criminal behavior. Included in this category are children that develop emotional and behavioral problems because of living with a mother who has mental health issues.
  
  

Criticisms

• Using biology as an excuse for crime leads to more lenient punishments.Comstock/Comstock/Getty Images
  
  Historically, the study of biology as a criminal factor was associated with eugenics, or the study of the controlled improvement of a race or breed by using inherited qualities. This brought condemnation to the idea. Worry over eugenics is not as prevalent now, but there is still opposition. It comes primarily from the crime victims and the court system.