This is a very difficult question to answer...
At the time of the violent act that initiated the self defense I would probably feel nothing but adrenaline and the overwhelming need to survive.
Later I might feel regret or remorse thinking what I could have done different to prevent, avoid or change the situation. However just like anything else it would do no good wondering "what if" because what is done is done. You can't change the past.
On a lighter note I thought the following sort of relevant...
Katie Couric, while interviewing a Marine sniper, asked: "What do you feel when you shoot a terrorist?"
The Marine shrugged and replied: "Recoil."
Short answer, "No"
Long answer: When I first started deer hunting I did wonder how I would feel about shooting a defenseless deer. My families has always had pets, dogs, cats, horses, etc and usually hold them in high regard as members of the family, so could I actually pull the trigger on a Bambi?
Well when I finally got a chance, I had no trouble shooting, did not feel bad about it. Keep in mind this was a cute deer that was not threatening me or my family in any way.
Could I shoot a scumbag that is intent on harming me or someone I love. You betcha! I am sure I would feel no more remorse than they would after harming me! (NONE what so ever!) I did not ask them to attack me, I in no way provoked the attack, they made a conscious decision to attack me, knowing full well the possible outcomes. Granted they probably did not expect me to fight back with a gun, but thatís just poor thought process on their part.
For the short answer:
Not everyone would develop PTSD, and if it came across like I was saying 100%, that wasn't the intent.
Some people will have the ASD and it will fade naturally with no further issue. It's somewhat like a car accident. The first time you drive after being in one, you may drive a little slower, look in your mirrors more, leave extra room when following, etc. After awhile though, you'll get back to your normal driving habbits.
For SOME though, if they do nothing to deal with having killed someone, it can and will come back to haunt them. It's easy before hand to say "If he's threatening me, I can kill him. No problem." After the fact, a fair number of people will second guess their actions. This is even more likely in our society where everyone wants to armchair quarterback with the benefit of hindsight. That second guessing, coupled with a myriad of other factors, is what leads to PTSD.
By recognizing the ASD following the incident, and dealing with the mental/emotional aftermath of the shooting immediately, it significantly reduces the likelihood of PTSD.
Don't take my word for it. The information is out there, and it's not written by touchy, feely people, it's written by people who do it for a living.
Highly recommend starting with LTC (Ret) Dave Grossman's books.
By putting someone else in a position where lethal force would be necessary, he has already proven he has no regard for his own life.
The play out of the situation itself comes down to training and what is needed to survive.
And your wife has a perfectly valid point, for the rate that school age children are getting shot up in the city of Chicago, he'll likely see a bullet, he'll likely see gang violence before that probation is over.
As to the lack of sense of responsibility it's not just an age thing and it's not just a Chicago thing, there have been many folks who have no sense of ramifications to their actions, just watch a weeks worth of those mock court TV shows and you'll see a large spectrum of people who blame someone else.
Life/survival with emotional scarring would be preferred over helplessness/death I would think, by most everyone.
To possibly have a moment's hesitation at the thought of killing another human being, no matter what the situation, is perfectly normal.
I'm 100% sure that I wouldn't have a problem defending myself or my loved ones from a life threatening situation, and would do what needed to be done to ensure our safety. I wouldn't have a problem choosing my life over some scumbags life that wanted to do harm to me, and I don't think that I would have any hesitation doing so...having assed the situation to be justified in doing so. Having said that I feel that I wouldn't have any emotional scarring from the insident. I have never killed anyone before so I cannot say for certain that I would not have a problem with it...and most people couldn't. Being in a war situation and having to go through such a thing gives some people the answer to that question. Most of us do not know the toll it would take.
At the beginning of our class to get a concealed carry permit, the Sheriff Deputy asked point blank, "would you have any second thoughts about taking the life of another human being with your firearm?" If so, you may want to think twice about getting a permit and carrying a firearm.
There were the brave responses of he** yes I would yada, yada. I thought for a moment and got angry at the scenario of some punk putting me into the situation whereby I need to shoot and possibly kill him. Would I do it? Would I regret it? Would it bother or haunt me? Yes on all three questions.
I would do it push come to shove because of my strong urge of self-preservation. I know that someday I will die, but not letting someone else decide that for me.
I would regret it in the fact that someone made the decision to remove themself from the human race and be what they are and forced me to end their existience. I don't wake each and every day thinking I will have to engage in such a scene.
It would haunt me because we all think and feel that human life is precious but it would not ruin me or make me feel that I was to blame. Eventually I would get over it and return to a normal life.
In the late 1980's I was involved in a SD shooting - I fired one round - striking the BG who was intent upon robbing us (small family store) and kidnapping my wife. I tried repeatedly to talk him out of it and in the end he left me no choice - I lost sleep over this for a couple of months (I think it was mainly due to continued threats by his family and loss of contact with my friends who were firefighters and local cops - they could not speak to me due to ongoing investigation and DA's slow reply in "no charging" me) .
I took the time afterward to re-evaluate my beliefs and re-assess the situation n the world, I probably have a better idea than most what my response would be in the future...
I've had dogs all my life so I don't believe that to be true.
He told me he shot a rapist several years back. Told me that he still has nightmares and has stopped carrying.
If you have a conscience, morals, respect for other human life, it will haunt you--- even if you were entirely legally justified.
I've never felt bad about physically defending myself, and I've hunted since I was a teenager, so no, I don't think I would have emotional trouble shooting someone who was threatening me or mine to the point I was justified in shooting them.
If someone has forced me to pull my weapon out in self defense, in my mind they have forfeted there life and thats that.
I guess I'll go against the grain here, but...
I think that I would have an issue in dealing with the shooting of another human being.
I like to think that this is what makes me inherently better than the criminals. The voice that would whisper, "Perhaps you could have...", or, "Maybe if only...", would give me pause to think, but I am ultimately confident enough in myself and my training to know that I would do the right thing. Hence my choice to continue carrying.
Without that voice, we lose something very important.
I call it my Humanity.