A troubled teenager murdered his own mother, who adored him and who always took his side, by stabbing her 29 times.

On the day of the killing, 17-year-old Marcin Jakubowski had put in a search term on the internet asking: “How to hold a knife properly in combat?”

That afternoon when she arrived at the family home in Watford from her cleaning job, her beloved son carried out what a judge said was a “ferocious attack” with a large kitchen knife.

Sentencing Jakubowski to a minimum term of 13 years and 223 days, Judge Michael Kay said: “Before your mother died, she must have suffered terrible mental anguish that she was being attacked by the son she loved and who she believed loved her.”

The teenager, who is now 18, appeared at St Albans Crown Court on Friday to plead guilty to the murder of his mother, Djolanda Jakubowski, 50, at the family home in Clarke Way, Watford on the afternoon of December 16 last year.

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Police cordoned off a house in Clarke Way, Watford in December 2019. Photo: UGC

The court heard how he lived at the family home with his Polish parents and a brother.

He had dropped out of education, didn’t have a job and was a loner with few friends, preferring to spend most of his time in his bedroom listening to heavy metal music, watching violent films and reading about weapons.

Prosecutor, James Lofthouse said while the teenager had come to dislike his brother and his father, who was threatening to throw him out of the house unless he got a job, he was very close to his mother.

The court heard on the morning of December 16 last year the defendant’s father and brother left for work as usual.

The mother left shortly afterwards for her cleaning job at a nearby hotel.

That day, the boy had a job interview at a restaurant in Watford but he was unsuccessful.

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The manager who interviewed him thought he looked “tired and unkempt”.

Jakubowski returned home and when his mother finished her cleaning shift at 1.30pm that day, she walked back to the house.

Mr Lofthouse said at about 4.50pm a neighbour heard a brief scream from a woman and what was thought to be the sound of chairs scraping on a floor.

Shortly afterwards the teenager made a 999 call, telling the operator: “I need help. My mum just killed herself in our house.”

Over the phone, the boy gave an account that she had called him downstairs and had started to stab herself and he had been unable to stop her.

When paramedics arrived at the house, Jakubowski answered the door covered in blood and “behaving erratically”, said Mr Lofthouse.

A blood stained bucket and mop were found nearby and bizarrely he claimed he had been lying with her in the lounge for four hours.

The court was told the mother had been stabbed 29 times about her face, head, chest, neck, abdomen and back.

In addition, she had suffered defence wounds to her hands and fingers.

It was soon established that the position of some of the wounds meant they would have been impossible for her to have inflicted them on herself.

The teenager was arrested and when his tablet was analysed his internet search history made for shocking reading.

Mr Lofthouse said in the weeks leading up to the killing, the teenager had put in search terms such as: “Can you buy a gun in the UK”, “What could kill you instantly”, “Deadly medical pills and can you buy cyanide”, “Easy ways to kill someone”, “Easy ways to murder someone”, “How long will you get for three murders”, “I hate my family”, and “I want to kill my family”.

Read more: Trio accused of stabbing man in 20s will face trial in court

On the morning of his mother’s murder, he had typed in as a search term “How to property hold a knife in combat”.

The court was told the boy had used a large kitchen knife to stab his mother to death, but why he did so remain unexplained.

Following his arrest, he refused to talk about the killing with the police officers and later to a psychiatrist.

All he would say was that they had argued.

When asked by a psychiatrist what it was about, all he would say was: “This and that.”

But it had been concluded the teenager did not meet the criteria for an insanity defence and would have been fit to stand trial.

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Djolanda Jakubowski, 50, was found with stab wounds at her home in December last year

Although a personality disorder had been diagnosed, the court was told it was a something that would not have played any part in the commission of the offence.

Judge Kay was told that because the boy had refused to talk about why he had killed his mother, his father and brother still had not been provided with any explanation as to why he had done what he had.

Even so, the court was told that they both still love him and hope one day they can be reunited as a family once more.

Passing a life sentence, Judge Kay told Jakubowski: “Every murder has one or more elements which are shocking, but few are inexplicable.”

He said this murder was not only “extremely shocking” but despite the efforts of a psychiatrist to explore the motive, it remained unexplained.

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The judge said: “All the evidence indicates you were adored by your mother you had an extremely close relationship with her.”

He said if other members of the family ever criticised the boy, his mother would always take his side.

The judge said the search terms uncovered by the police were telling.

“It is clear you were considering and planning the murder for some time. You were exploring different ways of committing murder and what the sentence might be. Far from being a fantasy, this was a shocking reality.”

He said the attack on his mother had been “sustained and ferociously violent”.

The judge then told Jakubowski: “You are a potentially highly dangerous individual.”

He ordered that the teenager should be “detained at Her Majesty's pleasure” for a minimum term of 13 years and 223 days before the parole board can decide whether it’s safe for him to be released.