The judge reminds jurors that the defendant told them Mrs Williams was “lying” when she said he had stabbed her in the head, and that he had not known at the time that she suffered a head injury. He reminds them that the defendant told the court he “struggled” rather than giving up the knife because he didn't want to get into trouble.

The judge reminds the court that when asked, the defendant told the court he was remorseful for what happened.

That concludes the judge’s summing up.

The judge tells the jurors he won’t send them out to begin their deliberations now, but will do so on Monday morning. He tells them to put the case out of their minds as much as they can, and tells them to come to their deliberations afresh after the weekend.

The trial will resume on Monday.

Judge Thomas reminds the jury that it’s the defendant’s evidence that he took the knife from the kitchen on the morning of February 5, and that he took the biggest one as it was the most impressive.

He says the defendant told the court that he hid the knife in the bag and planned to show it to his friends in school but wanted to do it when everyone was together as a group. He says in response to questions the defendant accepted that stabbing someone in the head with a knife could kill them.

The judge said the defendant told the court that February 5 was the first time he had taken a knife to school

The judge now turns to the defendant’s cross-examination.

He reminds the jury that in response to questions from the prosecution barrister the defendant told the court that he went “no comment” in his three police interviews because he was in shock and couldn’t remember what had happened. He reminds the jurors that the defendant told them his memories of the incident returned some two-to-weeks later.

The judge reminds jurors that the defendant denied there had been a plan to kick-in Mrs Williams’ door on February 3, and denied the teacher had been “targeted” in any way and that he and his friends had simply been "wandering around the school”.

The judge reminds jurors that the defendant accepted his mother had been upset about him not going to lessons on February 4 and took away his phone and banned him from going online as punishment, but that he said he wasn’t angry about it.

The judge reminds the jury that the defendant told the court he left school after the incident and went to his nan’s house, and that though he couldn’t remember saying something about “his head going” he said his nan wouldn’t tell a lie.

The judge reminds the jury that the defendant told them he went “no comment” in his police interviews on the advice of his solicitor.

The judge reminds the jury that the defendant accepted the teacher looked “shocked” at seeing the knife with “her mouth open and her eyes wide” but denied “lunging” at her. He says the defendant said Mrs Williams told him to give her the knife but that he refused because he didn’t want to get into trouble.

The judge reminds the jurors that the defendant then described how Mrs Williams had tried to grab the knife with both hands to take it off him, and how the knife “went everywhere” in the ensuing struggle. The judge says the defendant was adamant that the teacher was sat down throughout the incident, and says he told the court that he did not know the knife had come in contact with the teacher’s head.

He says the defendant then explained how Mrs Williams had been screaming and how it “all got too much” and he dropped everything and left the classroom. He says the defendant denied wanting to hurt the teacher.

The judge now reminds the jury about what the defendant said happened on February 5. He says the defendant told the court how he had walked into the classroom without saying a word, and approached Mrs Williams who was sat at her desk.

He says the defendant told the court he asked the teacher for help and that as he was going through his bag looking for a rubber, Mrs Williams saw the knife. The defendant said the teacher told him to take the knife out and hand it over, and that he refused.

The judge now turns to a summary of the defendant’s evidence.

He reminds them that the defendant told the court he did not have the knife on him in order to injure Mrs Williams, and told them there had not been any kind of falling out between him and the teacher.

He says the defendant told the court that he and his friends would take "random stuff” to school such as household items in order “to see what we could get away with”, and he says he planned to show his friends the knife,

The judge says the defendant accepted he had previously stolen tools from the school workshop and said it was a “game”.

The judge reminds jurors about the accounts Mrs Williams gave to police officers and paramedics who attended the scene.

He says the teacher told the officers that the defendant had tried to “get behind her” and had attacked her with a knife. He says Mrs Williams told one of the police officers she wasn’t sure if the defendant had hit her with the handle as there had not initially been any blood, but that she told other officers she had been stabbed.

The judge reminds the court that police went to the defendant’s home but he was not present, and that he was subsequently arrested at his grandmother’s house.

The judge reminds the jury that the defendant was interviewed three times with an appropriate adult present, and that he answered “no comment” to all questions asked.

The judge now reminds the jury about the evidence of forensic pathologist Dr David Rouse who told the court about the “linear incised wound” to Mrs Williams head which, he said, had been caused by a sharp blade.

The doctor told the court the wound was “in keeping with a stabbing action going into the head” and said it was “very difficult to get a penetrating wound through the skull” given the thickness of the bone, and said he had not seen one in the last 20 years.

The judge reminds the jury about the evidence of the "superficial incised wounds” to the teacher’s fingers and palm which the witness said were “typical of defensive injuries” consistent with an attempt to grab a blade.

Judge Thomas tells jurors there is no evidence one way or the other about any damage or lack of damage to the point of the knife before it was taken into the classroom, and he tells them they will need to be careful when it comes to considering this matter.

The judge reminds the jury Dr Rouse was not able to give any evidence about how and when the tip of the blade was damaged, and he tells the jurors not to speculate about the condition of the knife.

The judge now reminds the jury of the evidence of various teachers and staff members at Miford Haven School who spoke to Mrs Williams in the aftermath of the incident. He says the teachers described Mrs Williams as “crying and in shock”.

He reminds jurors of how Mrs Williams told her colleagues she had been attacked with a knife by the defendant, and how she had grabbed the weapon in self-defence suffering injuries to her hands in the process.

He reminds the jurors that the school was put into lockdown following the incident, and how Mrs Williams was given first aid and the emergency services were called.

The judge says a number of the teachers described the defendant as a pupil who had “flown under the radar” at school but how concerns had been raised about the peer group he had been associating with in recent times.

The judge says in cross-examination, Mrs Williams denied she had seen the knife in the defendant’s bag, and denied asking the defendant to hand it over. The judge tells the jurors it may be an issue for them to consider what circumstances the knife was first produced from the bag.

He says she also denied that the look on the defendant’s face was “vacant” but insisted it was “evil”.

Under cross-examination the teacher denied she was mistaken about what had happened, and said she has to re-live what happened every day.

The judge says the teacher then described how the defendant pulled a knife from his bag and “lunged” at her, knocking her down into her chair with the force of the blow.

He says the teacher said at first she did not know it was a knife but then saw the blade and thought she was going to die, and that she then grabbed the knife and a struggle developed. He says Mrs Williams described the look in the defendant’s eyes was one of “pure hatred” and how he tried to hit her with the blade again. The court hears the teacher was “screaming blue murder”.

The judge says the defendant then ran off leaving the teacher with the knife, and the teacher sought help from colleagues telling them she had been attacked.

The judge tells the jury he will summarise the evidence the court has heard - he says the recap will not be word-for-word, and says it is a matter for jurors what evidence they consider important, and a matter for jurors what weight they attach to the pieces of evidence.

The judge starts with the evidence of the teacher Vicki Williams, and reminds the jurors how she described the defendant coming into her room to ask a question about work which was something he had never done before. The teacher described him as demeanor as “cool and collected” and she said he was respectful.

He says the teacher then said the defendant closed the door and seemed to be trying to “circle” behind her while keeping her talking and “ruffling” through his bag. The teacher says her “Spidey senses” told her something was wrong and she thought he may be going to pull a knife but dismissed that thought as paranoia. The teacher says she asked the defendant several times if he was okay.

The trial resumes after lunch.

Judge Paul Thomas KC tells the jurors that matters of evidence are for them and them alone, but says it may be that there is a fundamental issue they need to grapple with - namely, did the defendant take the large knife into Vicki Williams classroom because he had not previously had chance to speak to her nor had the chance to show the knife to his friends in “some sort of bravado”, or did he take the knife into the classroom in order to harm the teacher.

He says if the jurors find the stab to the head was deliberate, they need to consider what the defendant intended to do.

The barrister says it is a “hell of a leap of faith” to go from the defendant not liking school very much to coming up with a plan to kill a teacher he had no issues with. He says the lack of evidence of any motive and the lack of evidence of any planning militate against being able to say the defendant intended to kill.

The barrister tells the jurors to “assume nothing, evaluate everything” and to approach the evidence with an open mind. He reminds them that the defence do not have to prove anything, and that that prosecution has to make them sure.

Mr Roberts says: “Give the evidence careful scrutiny with this ‘golden principle’ embedded in your mind - before you convict you have to be sure. Nothing else will do”

He tells jurors if they have a doubt, they should find the defendant not guilty.

That concludes the closing speeches. The court breaks for lunch.

The barrister invites the jury to consider all the evidence they have heard and to ignore the “emotive” language used by the prosecution. He invites jurors to find they “simply cannot be sure” what happened in the classroom was a deliberate act, and says there is “room for doubt”.

He says while you cannot look inside someone’s head, looking at the evidence in its totality there is “insufficient evidence to show he [the defendant] intended to kill or cause serious harm.

The barrister reminds the jury that “it simply cannot be said” how or when the tip of the kitchen knife came to be damaged, and that the court cannot be sure it happened during the course of the incident.

He reminds the jury of the evidence of the forensic pathologist they have heard from that he was not able to rule out the possibility that the injuries suffered by Mrs Williams were sustained during a struggle, which is what the defence say.

The barrister invites the jury to consider the background to the incident, of the defendant being part of a “delinquent friendship group" and of the “insecurities and misplaced loyalties” experienced by a 15-year-old. He says this is an important aspect the jury has to consider.

He says the defendant had no history of being violent, and says what happened was “out of character” for him.

The barrister asks the jury not to hold the defendant’s “no comment” interviews against him, saying if ever there was somebody who would follow legal advice it would be a 15-year-old boy who was in police custody for the first time and who was frightened.

The barrister says the defendant didn’t lose his temper in the witness box and maintained his version of events even in the face of lengthy cross-examination by an experienced Kings’s Counsel - “a David and Golliath battle”.

The barrister says the prosecution has been unable to prove any motive or planning, and he puts it to the jury that it is a “massive leap of faith, of imagination” to go from the events of February 3 to the defendant wanting to kill Vicki Williams on February 5, and he says the prosecution case “does not add up”

Mr Roberts says: “We say [the defendant] had no reason whatsoever to want to harm Mrs Williams, and that is a fundamental feature which you cannot get away from”.

The barrister says on any view taking a knife into school was an unwise thing to do on the part of the defendant, but he reminds the jury they are dealing with a defendant who was 15 at the time of the incident and he says the defendant is not the first 15-year-old to do something unwise.

The barrister says the prosecution has made much of the events of February 3 when a friend of the defendant kicked-in the door of Mrs Williams’ classroom.

He says the suggestion that the defendant somehow decided to “up the ante” from that incident to carrying out the motiveless killing of Mrs Williams is “almost not worthy of comment” and shows how the prosecution is “struggling to find any motive”.

The barrister adds: “The lack of any demonstrable motive is an issue because, as night follows day, it goes to intent - or lack of intent - to kill Vicki Williams”

The barrister tells the jury that while the prosecution do not have to prove a motive, the lack of one is a “fundamental and striking feature” of the case. He says there is no recorded history of any conflict or animosity between the defendant and Mrs Williams, and no evidence of any planning.

He tells the jurors there is a “pattern of uncertainty” in regard to the prosecution evidence, and he says they do not have to consider that Mrs Williams was lying in order for them to find the defendant not guilty if they have a “nagging doubt” about what happened.

The barrister says there was no evidence of any planning on the part of the defendant. He says there is no evidence the defendant had placed the knife in his bag the night before the incident as the prosecution had suggested. He says there is no evidence from the defendant’s phone of any planning or any relevant discussions with friends.

The barrister asks the defendant to consider the deterioration in the defendant’s behaviour in the period before the incident, and asks them to consider the events of February 5 in the context of the “delinquent friendship group” he had started hanging around with.

He invited the jury to consider why, if the defendant was planning to carry out a murderous assault, he had not concealed the knife under his top or jacket rather than having to “ruffle” through his bag.

The barrister invites the court to consider the varying accounts of whether Mrs Williams was sat down at her desk or was standing up when the defendant entered the classroom, and asks them to consider which makes more sense to them.

He reminds the court that the defendant’s name had been typed into the teacher’s laptop which was on her desk.

Barrister: “We say there is a real element of doubt as to whether she was sat down or standing up when [the defendant] came in. That is important. That about where the head injury was.”

Matthew Roberts KC now addresses the jury for the defendant.

The barrister says in any view what happened - a pupil taking a knife into school and producing it in whatever circumstances - would have been a terrifying matter for the teacher to deal with.

He says the location of the head injury is “curious” on the prosecution case, and he invites the court to find that the injuries to the head and hands is not just consistent with the defendant’s version of events but supports it.

He says the reality is, given the relative size and strength of the defendant and Mrs Williams, if the defendant had wanted to kill the teacher he could have.

The barrister says it is the prosecution case that Mrs Williams was stabbed and that there is no explanation as to why she would lie about it. He says when the defendant delivered the blow to Mrs Williams’ head he was aiming to incapacitate her and to kill her, and that it was only the fact that she fought back and screamed that stopped that happening.

The barrister says had the teacher been incapacitated by that first blow “we could be here considering a different offence”.

The barrister tells the jurors that when they consider all the evidence in the case they will come to a guilty verdict.

That concludes the prosecution closing speech

The prosecutor says: “It is does not, mercifully, matter that the injuries were caused were less than intended. That is only because he struck her in the back of the skull, it bounced off. The tip of the knife is not going to be damaged from accidental contact, is it. Matter for you.

“She fought for her life. When he struck her that blow with the knife, what was he intending? The only reason she is here is because she fought back”

The barrister says it is the prosecution case that when the defendant delivered the blow with the knife it was planned, and that he intended to kill.

He adds: “It is because he struck the back of the skull and she fought back that she is here to tell you what happened”

The barrister reminds the jury that the defendant fled the school after the incident and went to his nan’s house where he told her “something went in his head”. He says the defendant later claimed he could not remember saying that but that his nan would never lie. He says the reality was the defendant knew “he had done something terrible”.

The barrister reminds the jury about the defendant answering “no comment” to all questions asked in his police interview and later claiming that was because he could not remember what had happened. He says in reality the defendant “had not yet made up his story”, and that is why he said nothing.

The barrister also reminds the jury about the consistent accounts Mrs Williams gave colleagues, paramedics, and police after the incident - not that there had been “some kind of accident” while she was confiscating a knife, but that she had been attacked.

The barrister reminds the jury about medical evidence they have heard about penetrating wounds to the back of the head being rare because that is where the skull is at its thickest - but he says the defendant would not have known that.

Barrister: “That the blow struck the back of the skull is why the injuries were not as bad as intended by [the defendant]”

The barrister says the defendant’s account that the injury to the back of the head was caused during a “melee” as the teacher had hold of the knife and was trying to take it off him is “absurd… impossible”.

He adds: “There is a simple explanation. [The defendant] cannot explain the injury because it is inexplicable on his account”.