Sabah Khan, 27, pleaded guilty to the murder of her sister Saima, 34.
Chilling footage reveals the moment a woman tries to convince police that she had tried to save the life of her dying sister - minutes after she had stabbed her to death.
Officers are shown arriving at the family home of Saima Khan to find her sibling Sabah outside, seemingly distraught after discovering her sister's body.
When a police officer asks why there is blood on her arm, she claims to have wounded herself on "glass", which was shattered on the floor after a supposed break-in.
Sabah, 27, was jailed for life yesterday after she launched a 23-minute knife attack on her sister at their Luton home in May last year after luring her home from work.
She had been having a four-year affair with Saima's husband Hafeez Rehman, who revealed his "shame" over the adulterous relationship and that "not a day goes by" that he doesn't "regret it".
Sabah lured her older sister home under the ruse her children were crying, before slashing her throat with such ferocity she almost decapitated her.
Over about eight minutes, Sabah chopped off her sister's hand and pulled off her clothing to continue stabbing her as she lay dead, while her children were upstairs.
Some of the children woke up as the "scene of carnage unfolded" and Saima's 7-year-old daughter shouted down to her aunt: "Are you killing a mouse?"
Sabah Khan had been in a relationship with her sister's husband for four years and they had been having sex in his taxi and their home when his wife had gone to work.
He was 21 when he met Sabah, and she was just 10.
The court also heard how the younger sister had had an abortion after becoming pregnant by Rehman.
Rehman had taken advantage of the opportunity to sleep with the siblings and gain "exclusive rights" over his sister-in-law, the Old Bailey heard.
Rehman said: "I feel complete shame about having an affair with Sabah. I never imagined anything like this would ever happen. Sabah's actions have left our four children without a mum.
"I have four beautiful children but I have lost my world and I cry every day. Saima was there for all four children. She did everything. There is not a day goes by when I don't regret my affair with Sabah."
Sabah, who had bought a knife from a Tesco store two days earlier, waited until most of the family were out of the house attending a funeral at a local mosque before texting her sister to say one of the children was crying and she should come home quickly.
Saima suffered 68 knife wounds in the frenzied attack, including severed arteries and a jugular vein and deep wounds to her arms, skull and face.
Other members of the family found the mother-of-four lying in a pool of blood when they returned late at night.
The court heard that their screams "rang out" across the neighbourhood.
Sabah tried to stage a burglary at the scene, smashing a window and interfering with jewellery before calling police claiming there had been a burglary and her sister had been murdered by an intruder while she was in the shower.
Detectives initially investigated her claims before arresting her eight days later when they found the knife in a bin bag in her bedroom.
On the night of the murder, Sabah remained at home to look after her sister's children - a 7-year-old daughter, two sons aged 4 and 2 and a baby girl, who had just had her 1st birthday.
Prosecutor Jane Bickerstaff QC said Saima left the house around 10.15pm to attend the home of an elderly woman in her role as a carer that night.
Half an hour later Sabah texted her sister to say one of the children was crying.
Bickerstaff said at 11.03pm, Saima Khan replied "On my way".
The court was told a CCTV system on a neighbouring property captured the moment Saima arrived outside her home and showed her entering the house at 11.07pm.
Bickerstaff said: "The lights were seen going on at the house.
"On entering the house, Saima turned on the downstairs hallway lights and 45 seconds later, the lights went off, so the downstairs was in darkness."
The prosecutor said that had been the moment Sabah Khan struck as she waited in the darkness.
Bickerstaff said: "She lay in wait for her sister and 45 seconds after Saima got into the house, she was murdered in the hallway.
"There is no evidence that she ever managed to leave that area by the front door.
"It was a vicious and sustained attack."
Bickerstaff told how WhatsApp messages revealed Sabah's bitterness as Rehman's interest in her waned.
She referred to her sister as "that b***h", and told Rehman: "If I could I would take my heart out and show you what you are for me.
"Nothing in the world can change my feelings for you. Not even you. Day by day my love for you gets stronger."
Bickerstaff said: "From February, all was not well with Hefeez Rehman and his affection appears to have been transferred back to his wife."
Around this time Khan searched the internet for "poisonous snakes", "how to hire a killer" and "16 steps to kill someone and not get caught".
She was also in frequent communication with a "fixer" in Pakistan and handed him more than £5000 ($9600) to have her sister "finished off".
She told the fixer: "Sorry to bother you again and again. My friend is really upset now Hefeez does not even look at her. He says he realises his mistake... You finish off Saima as quick as possible so Sabah can get her Hefeez back."
The prosecutor said there was an added time pressure as her sister and her family were due to move out later that month.
Jo Sidhu, defending, said Sabah was a lonely individual, had traits of mental health issues and had in the past cut and strangled herself.
"For the rest of her natural life [she] will live with what she has done. The remorse is something that will infect her for the rest of her days."
Sabah showed no emotion as she was jailed for life with a minimum of 22 years for the "astonishingly brutal" murder of her sister.
Judge Christopher Moss told her: "Not only did you intend your sister to die, but this was no spontaneous event.
"You enticed her to come home from work so that the killing could be carried out.
"You had decided that afternoon that murder weapon should be used, which had been purchased by you days earlier. You have for some time planned your sister's death.
"The killing was astonishingly brutal and the knife attack continued after the deceased must have lost her life.
"You killed your sister in her own home with her children upstairs. Further, you suggested falsely that you sister had been engaged in an illicit affair with another man."
Judge Moss said Rehman had been "somewhat manipulative" during the relationship, which had caused Sabah "some difficulty in her personal life".
Psychiatric reports revealed that Sabah was emotionally unstable and has a form of a depressive disorder.
Judge Moss said she now accepts her guilt "unreservedly".
An impact statement by Rehman was read out in court in which he said "My wife Saima was a lovely, caring and kind wife and mother.
"I feel completely ashamed about my affair with Sabah. I know the affair should have stopped, but I never imagined anything like this would happen. Saima was such a good mum. I try my best with the children, but I can never replace their mum."