JURORS were made aware of both men's criminal past and their use of weapons before they were asked to return a verdict.
Usually, a jury is kept ignorant of past misdemeanours of those in the dock. They are told by the judge the prosecutors have to convince them of a person's guilty and each defendant appears before them with a clean slate.
However, the Criminal Justice Act of 2003 allowed – in certain circumstances – prosecutors to inform a jury about a defendant's "bad character".
The legislation means a court hears "evidence of or a disposition towards misconduct"
Simon Laws QC for the Crown Prosecution Service successfully argued to be allowed to tell the jury of previous convictions of both Williams and Pemberton.
In March 2009 Williams was convicted of being in possession of offensive weapons – a hammer and golf club – in St Budeaux Square.
In August the same year he was charged with affray and criminal damage after intimidating a neighbour and making threats to kill by burning down the neighbours' housing with his children inside. The jury was told the neighbour had to move home but when he came to collect his belongings, Williams attacked him with a garden spade.
In June 2010 Williams was found in a public place with a five inch kitchen knife.
In March 2011 he threatened a bus driver in Wolseley Road with a kitchen knife.
The driver, who was on his break, had received abuse from a small group of youths which included Williams. As the driver got back on his bus, Williams followed him and brandished the knife saying: "I will stab you up, cut you up you pussyo" before lunging at the driver.
Fortunately the terrified driver was able to shut the doors in time.
The jury was told that on Christmas Eve, 2011 police were called about an argument in Torpoint between Williams and a young woman at an address.
Williams had threatened to stab the girl with a knife.
He was later found by police officers at a taxi rank in Ferry Road, Devonport, drunk and with a eight inch kitchen knife in his sock.
After initially pleading not guilty he was convicted of the offence in November 2012.
He was handed a 12 month jail term and told by the judge "The knives are getting bigger".
The jury was told Pemberton, pleaded guilty to battery after an unprovoked assault on a man on December 24, 2013 outside Jesters nightclub in Union Street. The court was told he "swore and taunted a male" who walked away. Pemberton ran up to him and punched him in the face.
A court report by The Herald saw the prosecutor explain how Pemberton had become aggressive initially to a group of revellers, shouting 'come on then, let's have it'. Pemberton went on to lash out at two police officers called to the scene.
Pemberton later claimed he was 'too drunk' to remember what was happening.
During the murder trial, he was asked why he carried out such an unprovoked attack, to which he replied the man he punched had "annoyed" him.
The jury in the murder trial were not told that in mitigation, his defence solicitor told the district judge Pemberton was a "young man of just 19" who had "put in an application to join the army".
The solicitor added: "if only the court could sentence to two years in the army, I think that would be sufficient for this young man".
At the time the district judge told Pemberton: "You are within a whisker of me saying that a custodial sentence is appropriate", before handing him a fine and ordered him to carry out 150 hours unpaid work.
In September 2014 Pemberton pleaded guilty to an offence which took place in June the same year after he was found to be in possession of a machete in Uxbridge Drive.
The murder trial jury was later told he had kept the machete down his trousers and did not pull it out.
The Herald's court report states that Pemberton had bought the machete from a friend which he wanted as a "decorative item" for his bedroom.
He was outside the Bull and Bush pub in Uxbridge Drive, Ernesettle to meet a friend. He showed the item to his friend "but", his defence solicitor said "kept it primarily in its sheaf. It was not fully removed and it was not brandished, nor were any threats made. He tells me he had no intention of using it."
The solicitor added that Pemberton: "essentially panicked when he realised the police were on the scene and disposed of the knife, in what was perhaps a realisation on his part of the trouble he was in".
In mitigation, the court was told he was helping to care for his mother who had cancer, ever since he lost his job at a quarry.
He was jailed by magistrates for four months.
He was released in November after serving half his sentence.
The jury were told that on December 15, 2014 Pemberton and three other young men got a taxi to the city centre.
The Herald has learned the trip came about following a Facebook exchange.
A witness walking home from a Christmas party later told police he saw two men running along the street, both looking scared and frantic.
Moments later he was confronted by four males asking him where the two other men went, saying they wanted to "teach them a lesson".
The witness told police they seemed "intimidating, confrontational, angry".
One of the men – Pemberton – had what the witness described as two 'butcher type knives' later found to be meat cleavers who said: "We're going to cut them up".
Video footage, taken from Anstis Street, clearly showed Pemberton brandishing the two cleavers, threatening a group of other men who passed by.
Pemberton was arrested the following day.
The murder jury were shown the dramatic footage and told Pemberton pleaded guilty to the offence of affray on October 19 this year.
A few days ahead of the trial The Herald asked Pemberton's mother Suzanne asked if she wanted to speak about her son, of his childhood, his hopes and dreams as a young boy and what may have led him to become him fascinated with knives and violence.
Mrs Pemberton declined to talk to The Herald.
Her only statement, offered forcefully, was: "My son never hurt no-one.
"What you printed in the paper was lies.
"The police told me what you printed was lies.
"We don't want to talk to you people. You just print lies.
"You will see the truth in court."
At the home of Williams, there was no answer the week before the trial.
While one next-door neighbour's home showed an assortment of bikes and scooters, the other side revealed a well-tended garden.
Each of the neighbours who answered The Herald's door knock blanched at the mention of Williams and made it plain they were fearful about speaking on the matter.
One man, in his 60s, shook his head worriedly at the mention of Williams and closed the door quickly saying: "No, no sorry mate, I just don't want to talk about him, I don't want to get involved."
Another neighbour, a young woman, responded similarly at the mention of Williams, her smile dropping immediately as she whispered: "I don't want to get involved."