I had misunderstood your statement about psychopaths being born that way due to genetics, thinking that you were saying all psychopaths are born that way due to genetic. But, in looking at it again, I figured out what you really meant: that those who are born psychopathic are that way due to genetics.
So, I share with you this revised thought. I would be inclined to theorize that, to a degree, you are correct regarding DNA, and yet, I believe that there are also things that can happen in the womb that might be able to damage the brain's development, given existing examples. A deficiency of folic acid can cause spina bifida and too much alcohol during pregnancy can do damage to the brain and even alter physical appearance, and there have been both medicines, such as antibiotics, and elements, such as lead, that have lead to birth defects so it then is proven that excesses and deficiencies cause a wide range of maladies, and among them could also be damage to parts of the brain, such as the frontal lobes, that control executive functions. Further, injuries from physical trauma in the womb can also cause damage to the frontal lobes, although the risk is lower than once the baby is born.
Just like strongly shaking a baby can result in a wide range of physical (such as cerebral palsy, seizures, spasticity, internal bleeding, and sensory organ malfunction) and mental (learning disabilities, intellectual problems, and emotional/behavioral issues) problems, babies, toddlers, children or even adults who suffer the right kind of injuries to the parts of the brain relating to emotional regulation, maturity and self-control could develop psychopathy or other mental maladies that are physically based. There are recorded cases where adults have suffered a serious head injury only to survive, but with a greatly altered personality. Here's an article on the topic: After Brain Injury: The Dark Side of Personality Change Part I.