Most go through life without murdering but it's not their conscience that stops them because they have no conscience. There's just something not wired correctly in their brains. I also believe they can't be cured.

i think we are all born the way we are.

They develop into hardened criminals but if they had lived in different circumstances they might have turned out differently.

It's not either or.
There are both genetic and environmental factors that can affect who we are.

My feeling is that genetic influences are not very flexible and can override environmental effects but the environment can still flavor the way the genetic tendencies express themselves.

Tokyo (AFP) —

A 16-year-old Japanese schoolgirl who allegedly confessed to decapitating a classmate kept a severed cat head in her refrigerator, a report said Tuesday.

The teen was arrested last week on suspicion of murdering fellow student Aiwa Matsuo, 15, after police discovered her dismembered body on a bed in the suspect’s home in the western Japanese city of Sasebo.

The grisly case has attracted major media attention in a country with one of the world’s lowest crime rates, as commentators search for answers to explain the teenager’s pattern of increasingly violent behavior.

Some reports have suggested the parents of the girl—who wasn’t named because she is a minor—desperately sought to have her hospitalized but were rebuffed.

http://www.japantoday.com/category/crime/view/japan-teen-murder-accused-kept-cats-head-in-fridge