The roots of the propensity to murder probably lie deeper than expected - at genetic and biological level. People who tend to bring the destruction of their fellows are different from others in some anomalies in their body.
Future criminals can be recognized even while six months old. Just then, the babies can see abnormalities in the limbic system - the emotional core of the brain.
This anomaly occurs in people who commit crimes when they grow up. In people who are not inclined to commit crimes, these deviations are absent.
Of course, that the child has any abnormalities in the limbic system is still not a guarantee that when he grows up, it will surely become a criminal.
Furthermore, aggressive behavior is associated with reduced levels of enzyme monoamine oxidase. Genetic structure associated with low activity of this enzyme is characteristic of about one third of humanity.
If a child with this type of genetic unit receives poor treatment in early childhood, there is great likelihood for the child to become a killer when he grows up.
If one of the sex chromosomes is doubled, it is also possible to make this man a murderer. Males have a pair XY, and serial killers - XYY. In women, instead of the standard set XX, there is XXY.