This is the moment Nathan Matthews, Becky Watts's step-brother, was caught on CCTV shopping for a power saw which prosecutors say he used to chop up her body after murdering her, a court has heard.

Matthews has admitted killing the 16-year-old but denies murder, claiming her death was unintentional.

Bristol Crown Court today heard from a worker from the B&Q store where Matthews went the day after he killed Becky and bought a £80 circular saw.

Kelly Lee, who works as a supervisor in the Bristol DIY store, told the court Matthews even queried the price on the power tool after confusing it with one on the next shelf.

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CCTV shows Nathan Matthews shopping for a power saw the day after he is said to have killed Becky Watts

Prosecutors say he used the circular saw to cut up Becky's body before her remains were stored in a shed

A shop assistant at the store said the killer questioned the price of the tool, which he said he needed that day

Ms Lee told the jury: 'He brought a circular saw, gloves, a face mask and goggles. It came to £88.40.

'He was carrying a blue box and a number of items. I recognised the blue box as a circular saw. I asked him if he had found everything he wanted and started to scan the items.

'I said how much it came to and the man disputed he price on the receipt. He said one of the items was not the price he expected.

'It was the circular saw. It had come up at £80. I saw a colleague, I called him over and asked him to check the price.

'My colleague came back and said that the cheaper price was a different saw next to it and the one he had was £80.

'I explained that to him and he said he needed it for that day. Normally at that point we would offer to call and check other stores but we didn't.'

Matthews's girlfriend Shauna Hoare is also charged with the teenager's murder.

A jury heard yesterday that the couple killed Becky at the teenager's house in Bristol before bringing her body to their home, where it was cut up with a saw and wrapped in clingfilm before being put in bags, boxes and suitcases.

The court was told today that a neighbour of the couple heard an unusual amount of noise coming from their home on both the day prosecutors say Becky died and the following day.

Sarah Webb, who lives next door to the couple, said she heard a noise which sounded like a suitcase being dragged across the floor.

She told the court: 'There was shouting and screaming between Shauna and Nathan.

'They were very, very quiet people. We never heard bumps or banging or people on the stairs. We often thought that they weren't actually in.'

The prosecution say Matthews later used the saw to chop up Becky's body before it was stored in a shed

A worker from the B&Q store said he thought the saw was cheaper than she quoted and the price was checked

The store worker said she didn't check stock at other shops because Matthews said he needed it that day

The following day, in the afternoon, Mrs Webb said she heard further noises from the flat.

She said: 'There was lots of running up and down the stairs very, very quickly, banging, slamming doors, scraping, furniture being moved, a suitcase being rolled across a wooden floor which was upstairs.

There was lots of running up and down the stairs very, very quickly, banging, slamming doors, scraping, furniture being moved, a suitcase being rolled across a wooden floor which was upstairs A neighbour of Nathan Matthews and Shauna Hoare describes the day after Becky was killed

'I remember thinking it was annoying because I wanted to put my little one down for a nap and with the banging she was finding it difficult to sleep.

'It sounded like the bed was being lifted across the floor, like something heavy was being dragged. It was unusual, we never heard anything from them.'

The prosecutor in the case, William Mousley QC, today refuted claims by Hoare that she was not involved in the killing or in the disposal of the body.

Despite being with Matthews throughout the week of Becky's disappearance, 21-year-old Hoare denies a string of offences including murder, claiming she was unaware of what was going on.

Mr William Mousley today said that defence was 'ridiculous' and insisted the killing was 'a case of two people very close, very together, acting together'.

Mr Mousley said: 'You can be sure this was no accident... this was not something that just went wrong.

'You can be sure that Nathan Matthews is guilty of murder and [Hoare's] proximity, her involvement and her behaviour and the sheer implausibility of her version of events on the evidence which is available and the ridiculous concept that she was in blissful ignorance of what was happening at the time.'

The court today heard from a boy who was one of the last friends to see Becky alive. Jurors were also read a statement from her boyfriend, Luke Oberhansli.

Becky Watts (left) was killed by her step-brother Nathan Matthews (right) at her home in February. He denies her murder claiming her death was not intentional

A wedding photo shows both of the accused, Nathan Matthews and Shauna Hoare, and victim Becky Watts. Becky's father, Darren Galsworthy, married Matthews's mother, Anjie

Nathan Matthews, pictured with girlfriend and co-accused Shauna Hoare, claimed he was trying to kidnap Becky to scare her. A prosecutor today rubbished claims by Hoare that she knew nothing about the crime

Police outside the home of Matthews and Hoare during the investigation. A neighbour told Bristol Crown Court she heard the sound of a suitcase being dragged across the floor the day after Becky died

Mr Oberhansli revealed the last text she had sent him, the day before she is believed to have died, read: 'I love you so much'.

Her boyfriend said he tried to contact her on the day she is believed to have died, but none of his texts were delivered.

WHAT HAS THE JURY BEEN TOLD SO FAR? SUMMARY OF THE EVIDENCE GIVEN DURING YESTERDAY'S OPENING DAY OF THE TRIAL In a shocking opening day of evidence yesterday, prosecutor William Mousley QC told the jury: - Investigators believe there was a 'sexual motive' to the crime. - Matthews and Hoare allegedly suffocated Becky at her home then took her body to their house in their car. Matthews later told police he strangled the 16-year-old during a struggle. - Her step-brother then allegedly bought a power saw and dismembered her body across her neck and above her knees, elbows and wrists. - The body parts were then wrapped in thick layers of clingfilm and stored in the shed of a friend. - A police search found Matthews's home was messy but the bathroom was 'completely clean', the prosecutor said. Becky's blood was later found in a fingerprint of his on a doorframe. - Matthews told police he wanted to scare Becky and 'teach her a lesson because she treated his mother badly'. - Matthews denies there was an intention to kill. Hoare denies all knowledge of Becky's death. Advertisement

He said he was worried and went around to her house.

As he knocked on the door Becky was already dead and her body lay in a car parked on the drive, jurors were told.

He was met by Hoare, who, after speaking to Becky's stepmother, Anjie Galsworthy, told him Becky was not there.

The boyfriend's statement said Ms Galsworthy said it was 'strange' Becky was not replying to texts.

He also told the court Becky 'always seemed happy' and 'was not moody'.

Another friend, at whose house Becky stayed on the night before she is believed to have died, said she was looking forward to seeing her boyfriend when she went home.

Jurors were also played the 999 call which Becky's father, Darren Galsworthy, made on February 20 to report his daughter missing.

When the call was played Mr Galsworthy and his wife were not present in the public gallery.

PC Lamorna Trahair, who went to the family home, said Matthews answered the door.

'Darren, Anjie, Nathan and Shauna all appeared genuinely concerned about her disappearance and all stated it was out of character,' she said in a statement.

The police officer said that after the check, she went back to the lounge and noted: 'Nathan and Shauna were expressing concern for her welfare.'

They also wanted to know what the next steps in the police investigation would be, PC Trahair said.

A Detective Constable Clare French told the court she went to Matthews and Hoare's home on the evening of February 23 in order to search it - but the defendants were not there.

She rang Matthews' mobile phone and spoke to Hoare, who explained they were going to her stepfather's home and would not return until the following day.

Det Con French said she was 'quite insistent' that she wanted to speak to them that night, so she and colleague Detective Constable Haley Matthews went to Hoare's step-father's home and spoke to the pair when they arrived.

Prosecutors believe Becky was killed at her house before her body was taken to Matthews and Hoare's home. The couple bought a saw and bags around Bristol. It is claimed Becky's body was taken to another house

The trial today heard from Becky's boyfriend, Luke Oberhansli, 17, who said she sent him a text message the night before she died, saying: 'I love you so much'

Becky's father Darren Galsworthy embraces a dark-haired woman outside of Bristol Crown Court

It was then that Matthews admitted he and Hoare had been at Becky's house on the day she was last seen alive. He said she had been in her room before going out and claimed he had 'heard the front door slam'.

'I LOVE YOU SO MUCH': MURDERED TEEN'S LAST TEXT TO BOYFRIEND Becky Watts sent a last text message to her boyfriend saying: 'I love you so much'. In a statement read to the jury, Luke Oberhansli said: 'I last saw her on Tuesday February 17. I went around to her house after I finished college. I went up to her room and played on the Xbox. She was playing a game on my iPad. She seemed normal. 'We were texting all day on Wednesday February 18. She was replying quickly until I said I was going to sleep. She said she was in a happy mood. The conversation ended at 11.19pm. 'I got a text at 3.52am saying 'I love you so much'. I was asleep so didn't reply. 'We continued texting the following day and everything seemed fine. The last text I sent was at 11.21am.' On the day of Becky's death, Luke grew concerned when she did not reply to texts. He went to her home to see if she was in and was greeted by Shauna Hoare, who told him they did not know where Becky was. He left the property unknowingly walking past Becky's dead body in the boot of Matthews's car, which was on the drive. Advertisement

The jury of 11 women and one man heard yesterday that Matthews has admitted killing his step-sister but denies murder. Hoare, who was pregnant at the time, denies any involvement.

Prosecutor William Mousley QC told the jury Becky was suffocated, 'despite her fighting for her life'.

He said the couple planned to kidnap Becky and had brought a stun gun, handcuffs, tape and a large bag to her home.

'In addition to their apparent dislike of Becky, there is good reason to believe there was also a sexual motive behind the scheme, arising from a shared unnatural interest in attractive teenage females, and that a foreseeable conclusion to it being carried out would either be Becky's death or serious injury,' he added.

Mr Mousley said: 'There followed a deliberate, carefully planned and grotesquely executed plan to cover up her killing.

'Following her removal from her home, over the course of the next few days, her body was cut up with a knife and a power saw, the parts carefully packaged and then moved to another address to prevent them being found and lawfully buried, where they were intended to be stored probably temporarily until a final solution could be found.'

James Ireland, 23, and Donovan Demetrius, 29, deny assisting an offender by helping to move Becky's body parts.

Jaydene Parsons, 23, and Karl Demetrius, 29, admit assisting and offender by storing Becky's body parts in a shed at their house, which was 80 metres away from Matthews and Hoare's home.

But insist they did not know what was inside the bags hidden in the shed at their home.

The trial, which is expected to last six weeks, continues.

Timeline of the killing: How a search for a missing girl turned in a shocking murder probe

Thursday 19 February - Just after 10:50am, Nathan Matthews and Shauna Hoare leave their home at 14 Cotton Mill Lane to go to Becky Watt's address at 18 Crown Hill. They stop at a Tesco Metro to buy some batteries, 'possibly for a stun gun', prosecutors allege.

At 11:03am, Becky Watts send her last ever text message to her boyfriend. Prosecutors say she was suffocated by Matthews then put in the boot of his and Hoare's car. They then stayed at the house before leaving sometime after 6:00pm.

Friday 20 February - At 12.20pm, Matthews goes to convenience store Rajani and buys two bottles of drain cleaner. At 1.15pm he goes to B&Q and buys a circular power saw, gloves, face masks and goggles.

Just after 4pm, Becky's father Darren Galsworthy rings the police and reports her as missing.

Becky's body was found by police in a shed behind the home of a friend of Nathan Matthews

Saturday 21 February -Just after midday, Matthews and Hoare went to Asda in the Bedminister area of Bristol and purchased, in addition to groceries, 'various bleach-related cleaning products', black bags, rubble sacks, rubber gloves and three rolls of cling film, it is alleged.

Sunday 22 February - The pair are caught on CCTV at the Broadmead shopping centre. They are captured in a 99p store at around 11.33am in Wilko at 12.01pm. They buy more rubble sacks and tape, as well as a sponge.

The pair then went to Sainsbury's in Brislington at around 14:05 and purchase more tape.

Monday 23 February - Police twice call on Matthews and Hoare at their home but there is no answer at the door and the curtains are drawn.

Posters were put up around Bristol after the teenager went missing in February this year

Later that night, at around 20 past 9, a five-minute call is made from Hoare or Matthews' phone to Karl Demetrius. A series of messages begin between Karl Demetrius, his colleague James Ireland, his brother Donovan Demetrius, and his girlfriend Jadine Parsons.

Tuesday 24 February - In the early hours of the morning, a van is caught on CCTV driving between Cotton Mill Lane and Demetrius' home at Barton Court – some 80 metres away from one another. The CCTV captures figures moving around and 'a large item' being carried.

Wednesday 25 February - Matthews tells his employer that he has 'family issues' and need four weeks off work.

Thursday 26 February - Matthews or Hoare's phone is used to browse newspaper reports about Becky Watts.

Crime scene investigators search the couple's home and discover blood on the doorframe. They are later both separately interviewed in a formal setting.

Friday 27 February - Forensic scientists search the couple's address and discover Matthew's fingerprints in one of the bloodstains, which DNA tests prove belong to Becky.

Saturday 28 February - Both he and Hoare are arrested on suspicion of kidnap.

Monday 2 March - The inquiry becomes a murder investigation.

At 9.45pm, Matthews admits to killing Becky and storing her body parts at Barton Close. He says he strangled her after trying to kidnap her.

Tuesday 3 March - In the early hours of the morning four people are arrested for assisting an offender and police discover several suitcases, a full bin bag, and a blue plastic box containing Becky's remains.

The trial continues