There is now a Youth version. Normally they seem to originally get a diagnosis of conduct disorder, i.e. your kid is a psycho when younger and in trouble.

The kids in custody would be easy to study, the ones living next door would be a much tougher thing. Probably couldn't even try to discuss this with the parents. Who would admit their kid could be the future Ted Bundy or a white collar criminal?

The conscience forms between 3 -5 years old.

Shockingly the general Population hasn't been figured out how many there really are. Personally I think the numbers are a bit low. Hare did the stats and that was the last one, no update since. I would think that kind of information being updated would be of interest to a researcher. Hare did his figures based on the prison population. I about fell off my chair when I confirmed this information awhile ago.

I believe the numbers are higher but it would be hard to determine them.
They use truancy and daytime crime comparisons to arrive at a figure. Then use the percentage of that figure. It would not be very accurate though because a lot of fledglings may not be truant. Especially if they have a fan club. Some I believe are showing high Psychopath traits are known as really good students. The news is loaded with stories of "he was such a good kid" reports following some shocking crime. You do not hear many "he was in trouble all the time" stories.

There is a website where you can see the homes in the US, that convicted Psychopath's lived in.
It says some things about their horrid crimes.

Gacy had his mother living with him, in his house during his murdering years,
his wife and kids moved out before he filled his house with victims bodies.

I remember a guy finally got caught taking his wife out on the lake and after she drowned he collected insurance and remarried. Then did this to the next two wifes before he got caught.
A witness actually noticed him moving his raft away from the overboard wife.

I have seen that look you describe. It is vacant. My parent had this look,at times. I hated to make eye contact with him. I seen the other side.
I spent my life raised by the Psychopath. My other parent used me as the bartering aid. She thought I was a security for her. She thought that he could not lie,cheat or do bad things with his own child in tow. She was wrong.
He was more dangerous, who would think a parent with a small kid poses any threat.
That false security is a victims connection to a perpetrator.
He had an alibi.
I am sure other Psychopath parents are out there using their kids, in full view.
One vacant look from a Psychopath will keep a kid quite too. Makes you feel a deep terror, frozen in fear.
Like a stranger is inside the Psychopath and just used his eyes to look at you.

The look a Psychopath gives you pushes your thoughts,truths beyond the sub conscious.
Your truth went in to a black hole. You wish you could escape with it.
Its hard to pull yourself together. It is fear.
You just faced death personified.
You wonder when he will return for your life.
His job symbolism is the reaper.
When he gets off work he goes home.