The boy, is one of three who have been accused of the murder of 26-year-old Peter Cairns on June 11, 2021, on the Silkin Way footpath near Stonebridge Close in Telford.
Another teenager has admitted murdering Mr Cairns and will be dealt with separately.
The three other teenagers, who cannot be named for legal reasons, are also charged with causing assault occasioning actual bodily harm to Kaine Bushell.
Philippa McAtasney, defending the boy who was 14 at the time of Mr Cairns' death, urged members of the jury to have "cool and dispassionate minds" and to look at all the evidence. The young man she represents has admitted being in a gang called the TF7s, and handling weapons including a wheelbrace which was carried on the day of the murder.
The boy has admitted striking Kaine Bushell once with the wheelbrace, but says he did it in self-defence after the 21-year-old approached him. The defence says it was in a threatening way and the young man was entitled to take a "pre-emptive strike" if he thought he was going to be attacked.
Ms McAtasney said it was "shocking and sad" to think of young men joining gangs or having weapons, as the young man has admitted.
"He has taken full responsibility for that and his guilt in another case," she said.
He had pleaded guilty to cutting "superficially" another boy who he knew but it had nothing to do with gangs.
"It is nothing to be proud of," Ms McAtasney said. "There was no really serious harm, it wasn't murder and he stopped and they walked away."
She told the court it did not mean that her client had any part in the murder of Peter Cairns. The prosecution says he was part of a joint-enterprise and bears responsibility for Mr Cairns' murder.
"He did not kill him," she said.
Describing her client as baby-faced, Ms McAtasney asked for the jury to treat him as an honest witness because he had given a "warts and all" account at the first opportunity.
As for the charge of actual bodily harm, she said the young man had struck Kaine Bushell in self-defence, and was not intending harm. "There was no knife and he stabbed no-one, there was no assault on Peter Cairns" she said.
Asking the jury why they should care, as they might consider her client "not worth it."
She said: "We live in a civilised society with a sense of fairness and justice. You represent society.
"You are not here to like my client on his behaviour in 2021 but you are not here to dismiss him without thought," she added.
"He admitted being in the TF7s and of having the wheelbrace but it does not mean he is guilty. True verdicts are based on evidence."
She said the prosecution had to prove beyond doubt that her client had committed the crime. "You must not convict unless you are sure," she added.
Ms McAtasney also threw doubt on the evidence given by victim Kaine Bushell. She said many of his answers had been that he could not remember.
"He is not automatically truthful because he lost his friend," she said.
Her client did not appear in the witness box, which was his right she said.
Her client says Mr Bushell had been "very frank and truthful" about thinking himself to be a member of a gang, although he is "no Mafia godfather." He had claimed that he had turned to see Mr Bushell staring at them, and responded to something he had said.
But they had not been out "on the hunt" and weapons were not out, and they had no intention to confront.
But things escalated and her client hit Kaine Bushell with a wheelbrace but only after her client had asked another defendant to "show him the thing" (a Samurai sword) to scare him off.
Her client had felt a "genuine threat" from Kaine Bushell, a taller and older man, and he felt "scared and nervous" and felt he had to hit him. He was "protecting himself" she said, and even though he had hit out first he was entitled to make a "pre-emptive strike" against the threat.
"He had instinctively defended himself against an older, bigger man," she said.
"What he did might be reasonable in the circumstances.
"It was one hit at half power and it caused a bruise. It didn't break his arm."
On Thursday Ms McAtasney intends to defend her client against the murder charge.
The trial continues.