Only three women in UK history have been sentenced to life in prison. Joanna Dennehy is one of them.

Three women in the UK are serving life sentences in prison. Joanna Dennehy is one of them.

Dennehy left home at just 16 years old and never returned. She would go on to murder three men and injure two more during a 10 day killing spree in March 2013.

According to her mum, Kathleen, Dennehy was a quiet, loving girl from a good family, but that began to change when she entered her teenage years.

“The girl that killed those people is not my daughter. My daughter’s that nice 16-year-old that never came home,” she says in the documentary Crimes That Shook Britain.

Kathleen says her daughter was kind and loving when she was younger, she keep good grades and she loved netball and hockey.

“She was very sensitive. If she stood on a worm or something she would be really upset if it died – she used to take them to bed with her. So she was a loving girl.

“She was polite to everybody. Teachers always said that she was a nice girl.”

But that all changed when Joanna met her boyfriend, John Treanor, who was five years older than her. She started drinking heavily, taking drugs and committing petty crimes.

She moved out with Treanor and had two kids with him. When they split up, Treanor gained full custody of the kids.

Joanna then embarked on a violent crime spree. She stole things, assaulted people and was arrested for brandishing a knife in public. She was eventually diagnosed as having an antisocial personality disorder and psychotic tendencies.

In March 2013, when Joanna was 31, she met Lukasz Slaboszewski, a Polish national. She sent him a series of suggestive messages and arranged for him to meet her at a property in Peterborough. When he arrived she stabbed Slaboszewski through the heart with a pocket knife.

She then murdered her housemate, John Chapman, and her boss and landlord, Kevin Lee.

Like Slaboszewski, she lured Lee to a house with the promise of sex, and then stabbed him five times, puncturing his heart and lungs.

Lee's body was found in a ditch the next day. He was dressed in a black sequined dress, which had been pulled up above his waist. Dennehy was immediately named as a suspect and the nationwide search for her began.

Meanwhile, Dennehy enlisted the help of 47-year-old Gary Stretch and went on a 'Bonnie and Clyde' inspired killing spree, travelling over 225 kilometers to Hereford.

Once they arrived in Hereford,  Dennehy and Stretch drove around looking for new victims. Dennehy stabbed two random dog walkers, Robin Bereza and John Rogers, both of whom survived their horrific attacks.

Dennehy seemed unfazed when she eventually arrested for the murders and she pleaded guilty at her trial. After she was arrested, doctors ruled that Joanna was suffering from paraphilia sadomasochism, which means she derived sexual pleasure from both giving and receiving pain and humiliation.

“When I saw this footage of Jo it was like somebody I didn’t know," Kathleen said. "She’s standing there being charged, smiling and laughing, that’s not the kind, loving Jo that was our baby.”

Dennehy was sentenced to life in prison and it was recommended that she never be freed.

Joanna has never given any reason for her 10 day killing spree, apart from telling a friend, "They shouldn't have pissed me off. They shouldn't have flirted with me".

Her family has now disowned her and they believe she's not the girl they once knew.

“To me she doesn’t exist any more. I don’t ever want her to come out of jail," Kathleen said.

"The world’s safer without Joanna in it."

The episode of Casefile you need to listen to.