Woman stabbed City banker partner after he said he had met someone else, court told

A woman fatally stabbed her City banker partner months after he told her on her birthday he had met someone else at work, a court heard.

Joanna Cierpka, 51, was arrested on March 15, 2026, when police found the body of 52-year-old Henrik Slotsaa at their home in Elephant and Castle after being called to the property having been alerted to welfare concerns.

Officers forced the door at 2.41pm and discovered the defendant injured in the living room, the Old Bailey was told.

Danish national Mr Slotsaa, who worked as a banker at Citibank’s London office in Canary Wharf, was found dead in a bedroom, and it was clear he had been dead for some time, Danny Robinson KC, prosecuting, said.

Polish national Cierpka was arrested and taken to hospital for treatment for her wounds.

At the hospital she told a member of staff: “I killed my partner”, which was recorded in writing, and she signed and dated the note, jurors were told.

She has pleaded not guilty to murder but she says she is guilty of manslaughter by reason of her diminished responsibility, the Old Bailey heard.

Stephen Lynn and his wife Anna Kotynska-Lynn said they became friends with the couple in about 2019, and Mr Lynn said at that time the defendant was the “life and soul of the party”, the prosecution said.

Cierpka was made redundant which affected her self-confidence, and she had previously received treatment and medication for depression, the court heard.

They met up for the defendant’s birthday on January 17, and Ms Kotynska-Lynn thought that although she was trying to be more like her old self, she was struggling.

In the following days they exchanged WhatsApp messages, and Cierpka said that she thought that Mr Slotsaa had had enough of her, and she thought they would soon be having a serious conversation about the future of their relationship, the prosecution said.

After her arrest, Cierpka told a psychiatrist that in December 2025 Mr Slotsaa had told her he did not love her anymore, and that on her birthday he told her that he had met someone else at work.

In late February or early March, Mr Lynn and Ms Kotynska-Lynn saw Mr Slotsaa briefly on his own and he mentioned to Ms Kotynska-Lynn that Cierpka was in a bad way, and that he had started to plan for a life after her.

By that stage, Mr Lynn knew that Mr Slotsaa had been, in Mr Lynn’s words, “flirting” with a work colleague called Aimee O’Shaughnessy, the court heard.

On March 8 Mr Slotsaa told Mr Lynn that he thought Cierpka had found out about Ms O’Shaughnessy, because she may have been looking at his phone.

Mr Lynn said that on the same day Cierpka just sat on her phone, scrolling, and he described the atmosphere as “strained.”

Ms O’Shaughnessy started work at Citibank in September 2025 and first met Mr Slotsaa at a work event on November 12, and they struck up a friendship.

In December they had lunch together and they swapped numbers.

Throughout January 2026 Mr Slotsaa and Ms O’Shaughnessy met up for lunch on a number of occasions. Mr Slotsaa told Ms O’Shaughnessy that things were not great at home, and he told Ms O’Shaughnessy that he liked her, the prosecution said.

She said that she did not want to complicate things by starting a relationship with him. According to her, he was fine with this, Mr Robinson added.

In the week of March 9 to 13, before the police found his body, his work colleagues became increasingly concerned about Mr Slotsaa’s welfare because he was absent from work and they could not contact him.

On March 13 one of Citibank’s security employees went and called up to the flat on the intercom and spoke to Cierpka, who said he had gone out.

Forensic pathologist Dr Ashley Fegan-Earl conducted a post-mortem examination on March 18 and said death occurred around March 9, although he stressed that he could not be precise about when Mr Slotsaa died.

The examination revealed there were 14 separate sharp force injuries. He noted wounds to the face, neck, arms and legs.

There were three injuries to the neck, one of which was potentially fatal on its own, jurors heard.

Stab wounds to the right index finger and the left forearm were, in Dr Fegan-Earl’s opinion, defensive injuries.

There were also wounds to the backs of both knees that may have represented an attempt at dismemberment, the prosecution said.

The prosecution said that in order to prove diminished responsibility, the defence must establish that each of the following four things are more likely than not to have existed: that when she killed Mr Slotsaa, Cierpka was suffering from an abnormality of mental functioning; and that her abnormality of mental functioning arose from a recognised medical condition; and that her abnormality of mental functioning substantially impaired her ability to understand the nature of her conduct and/or to form a rational judgment and/or to exercise self-control; and that her abnormality of mental functioning caused, or was a significant contributory factor in causing, her to kill Mr Slotsaa.

Psychiatrist Dr Penelope Brown, who was instructed to examine Cierpka by the defence, formed the view that at the time she killed Mr Slotsaa, Cierpka was suffering from an episode of severe depression with marked suicidal tendencies, such that it represented an abnormality of mental functioning from a recognised medical condition, jurors heard.

In Dr Brown’s opinion, the depressive episode impaired her abilities to form a rational judgment, and to exercise self-control. As a result, according to Dr Brown, the defence of diminished responsibility is available to Cierpka, the prosecution said.

The prosecution instructed another psychiatrist, Dr Shamir Patel, to examine Cierpka who concluded that she was not suffering from diminished responsibility when she stabbed Mr Slotsaa.

Although Dr Patel agreed that at the time of the killing Cierpka was suffering from depression, which is an abnormality of mental functioning arising from a recognised medical condition, he did not accept that it substantially impaired her ability to form a rational judgment, or to exercise self-control, the court heard.

Dr Patel also disagreed that her depression provided an explanation for her conduct.

In his professional view, the killing happened because she was angry with Mr Slotsaa, and jealous of his friendship with Ms O’Shaughnessy, set against a backdrop of the deterioration of their own relationship and her use of alcohol, the prosecution said.