"1234" was our code word for mentally ill or emotionally disturbed. Crazy. "I've got a twelve thirty-four..." We used to joke that their should be a "Two-four-six-eight" for the ones that were twice as crazy as usual.
Sometimes, teaching a Conflict Communications course, one of the students will be in a Mental Health field and will ask about dealing with the mentally ill, or a cop will ask about dealing with someone in extreme emotional crisis.  THat was my job for a long time.  There are techniques and stuff to know and ways to talk... but most of what I learned came from an attitude.
I admired these guys.  Understand that I was working with severely mentally ill people in a jail.  Mental illness is one thing.  Some (but not all) were also pure criminals.  Most, outside of the jail, were homeless.  How many people do you know, including yourself, that could handle being homeless?  Could figure out where to get food and shelter and clothes and the occasional shower?
Add to that that you can't even trust your own mind.  Not all of the things you see and hear are real.  You are sometimes compelled to do things you don't want to do or can't force yourself to do things you need to do...
"I know Sarge, I do better on meds and I'm happier when I'm on meds, but I can't make myself want to take them..."
And these guys (and gals) survived.  They didn't thrive, not by any stretch of the definition, but they survived.  Would I?  Dumpster diving and hustling would be hard enough, coming from my old-school pioneer stoic background (Stoics suck at panhandling) but not knowing if the person I was begging from was even real?
Every time I looked at the inmates in the Mental Health units, every time I was tempted to look down on them or feel superior, all I had to do was look at the other officers or counselors or nurses or myself and wonder if we would even have survived.
Same with criminals, and this is a weirder line to cross.  There are many, many violent criminals, some extremely depraved, that I got along well with.  To put it another way, there were a few that I would play chess with and listen to their problems and even counsel that I would shoot without hesitation if I saw them near my children.  As people, I got along with them. As predators, my job was to stop them cold.  It wasn't an either/or thing.  Both.  At all times.
Most, at least most of the ones I knew, were raised to be criminals.  Daddy a drug dealer and pimp, mommy a drug addict and whore.  Extended family and many friends and some of the neighborhood similar.  Sometimes you wanted to bang your head.  What was the rite of passage in your family/group to be a 'real man'?  First deer?  First time getting laid?
For one family I knew from jail, it was prison.  Not jail, jail didn't count. "Hard time" a violent felony and more than a year sentence were prerequisites to being a man.  They couldn't wait until they were eighteen and it became a possibility...
Raised in this environment, some profoundly antisocial things made sense.  Lying was constant, since giving up information in that environment was unsafe.  Trust is stupid.  Intimidation is fine but showing anger? When you felt anger you showed a smiley face and got a weapon.
Like a lot of officers, I don't believe in rehabilitation.  We simply haven't seen it work.  You raise a violent criminal's self-esteem he gets more, not less, violent.  I have enough background in psychology to be able to tell how individual studies were fudged.
But sometimes I think we made a difference.  When someone who had been raised to lie and con as the only effective ways, short of violence, to get what he wanted would start the long story and we'd say, "Eddy, you don't need to hustle me.  Tell me what you want and if it's within the rules, no problem.  You don't have to work so hard."
I don't know how many, if any, really changed.  But showing someone raised in the criminal subculture that there was sometimes a better way, that sometimes they could get what they want without lying, without pissing people off, that there was an effective solution that was safer...
They had never learned, growing up, that sometimes it was safe and effective just to ask.  That away from their family and friends and subculture people being out to screw you was the exception instead of the norm.
So, I don't think I ever rehabilitated anyone.  But teaching a few that there were less damaging ways that were safe and effective may have been small steps to habilitating a few.
"You can't rehabilitate someone who was never habilitated in the first place."-- Don't remember who said it, one of my instructors two decades ago.