A teenager who dared his friend to stuff a lit Megaburst firework through the letterbox of a house, killing the elderly occupant, has been found guilty of manslaughter.

Josephine Smith, 88, was believed to have been asleep in bed when the firework let off two successive explosions and set her home ablaze on October 28 2021.

On Friday, Kai Cooper, 19, was found guilty of her manslaughter, and arson with recklessness as to whether life was in danger.

Prosecutor Heidi Stonecliffe KC had told how Cooper was accompanied by a younger boy, now aged 17, when he visited a firework shop in Romford, east London, earlier that evening.

Cooper told the shopkeeper: “I want something that is going to go far and quick.”

He went on to tell his girlfriend outside: “Hey babes, come here. I’m trying to get fireworks, let them off at people. People are going to get terrorised tonight.”

Having paid for the fireworks, Cooper also bought two lighters from a Co-op shop, jurors heard.

He and his 17-year-old friend then walked towards Mrs Smith’s house in Queens Park Road, where she lived alone.

Mrs Smith “was entirely unknown” to the pair.

The prosecutor said: “It is a tragically random incident. That makes it no less serious or tragic.”

Josephine Smith death
The house in Queens Park Road, Romford, where Josephine Smith died (Ian West/PA)

Before reaching Mrs Smith’s home, the two youths set off some of the fireworks in the street, next to a restaurant and a pub, near cars, and even towards frightened pedestrians, jurors were told.

Ms Stonecliffe said: “They acted as a team as they did this, with Kai handing (the 17-year-old) the fireworks before they were lit and Kai encouraging (the 17-year-old) to do this.

“It was, it is suggested, the precursor for the altogether more tragic events that occurred shortly afterwards.”

The 17-year-old took a Megaburst firework and ran across the road towards Mrs Smith’s house, where she was in bed and likely asleep, the court heard.

Kai Cooper court case
Kai Cooper, 19, who was found guilty of manslaughter, and arson with recklessness as to whether life was in danger (Met Police/PA)

He then lit the firework and put it through the letterbox, jurors were told.

Ms Stonecliffe went on: “Two explosions occurred in swift succession, just like others that (the defendants) had set off in the street.

“They caused a fire to start, which burned through Mrs Smith’s house.

“By the time the fire service had arrived, the property had filled with smoke and Mrs Smith was found, already sadly deceased, in the upstairs bedroom of the house.

“Efforts made to revive her were unsuccessful and she was pronounced dead at 11.09pm.”

Cooper and the youth, who cannot be identified for legal reasons, had left the scene long before.

The prosecutor said there was no dispute that Cooper and the other youth bought fireworks and lighters that night, all paid for by Cooper, or that one of them was put through Mrs Smith’s door.

The only issue for the jury to consider is whether Cooper was party to the offences by encouraging and assisting the younger defendant, she said.

According to a statement from Cooper’s girlfriend, the 19-year-old had been laughing as his younger friend ran across the road to Mrs Smith’s house.

Ms Stonecliffe said: “It was her view that (the 17-year-old) would not have put the firework through the door if Kai had not suggested it.”

Cooper, from Leatherhead, Surrey, was remanded into custody and will be sentenced at a later date at the Old Bailey.

Detective Chief Inspector Linda Bradley, from the Met’s Specialist Crime Command, said: “This was a heart-breaking case concerning the needless death of an innocent lady, Josephine Smith, in her own home.

“The thoughtlessness of the actions which unfolded that night are incomprehensible, and tragically resulted in the most devastating consequences. Mrs Smith’s family continue to struggle to come to terms with their loss and our thoughts remain with them, especially today.”

Ms Smith’s son, Alan Smith, said: “Losing Mum in such a horrible way has haunted our entire family. Mum was so loved by all of us and had many more happy years ahead of her.

“To see justice done today may hopefully help us to begin to move forward very slowly.

“The issue surrounding the sale of fireworks to the public is a fight that we intend to continue. In addition, the irresponsible way those fireworks were sold on that night haunts all of us that have seen the footage.”