Legal: the egg shell skull rule

I remember sitting in the criminal law class that afternoon. It was 300 level first semester, a four (4) unit course. Everyone looked forward to the lecture as we had a wonderful lecturer. The Lecturer was one whose passion for teaching was on another plain. He patiently explained lecture notes to the understanding of everyone who cared to be present.
That day he lectured on the Eggshell skull rule, he so explained the \”eggshell\” rule, also known as the \”thin skull\” rule, He said it is one of the oldest and most well-established legal principles.
It was derived from custom and judicial precedent rather than statutes. It was used in some tort law systems, with a similar doctrine applicable to criminal law.
The rule states that, in a tort case, the unexpected frailty of the injured person is not a valid defense to the seriousness of any injury caused to them.
In another phrase, it means that the person who hit the eggshell-skulled person is responsible for the much greater harm caused by the hit, not just the amount of harm that a normal person would have suffered.
After about ten years, now in legal practice, I understood the implication of this rule. It was at a prison centre where I went to pick up some pro bono cases as part of corporate social responsibility or contribution to the community I reside.
I met a young man who was in his late 30s and the reason he was stuck in the prison facility was as a result of the application of the court based on the principle of the eggshell rule.
His story was pathetic, he had a misunderstanding with his friend that led to him slapping his friend, and to his amazement his friend fainted.
Ordinarily, a slap is not such that could cause serious harm to a person at worse it will be termed an assault, but that day, the odds were against him.
A mere slap put him on his toes, and he rushed his friend to the nearest hospital, but his friend never returned home, his friend passed on.
He was arrested and prosecuted for murder not for slapping a friend, he however was sentenced for man slaughter to serve for life as opposed to death by hanging.
The period between the arrest and the conviction took (5) years. Imagine a baby born and five (5) years after.
He had further stayed in the prison facility for over five years after his conviction as an inmate.
It took the intervention of the President who granted him a presidential pardon that brought him out of the prison walls after many years lost in prison.
A mere slap leads to the death of a person.
The big question is can he fit into society having stayed away for so long?