The Old Bailey has heard that Joanna Cierpka, 51, fatally stabbed her partner, City banker Henrik Slotsaa, 52, at their home in Elephant and Castle, south London, after he told her on her birthday that he had met someone else at work. Police found Mr Slotsaa's body at the property on Newington Causeway on March 15 2026, after being alerted to welfare concerns.
Discovery and Arrest
Officers forced entry at 2.41pm and found the defendant injured in the living room, the court was told. Mr Slotsaa, a Danish national who worked 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, according to Danny Robinson KC, prosecuting.
Cierpka, a Polish national, 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 admits manslaughter by reason of diminished responsibility.
Background and Relationship
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 had been 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 she thought Mr Slotsaa had had enough of her and that they would soon be having a serious conversation about the future of their relationship.
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 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 that Cierpka was in a bad way and that he had started to plan for a life after her.
Work Colleague and Events Leading to Death
Mr Lynn knew that Mr Slotsaa had been, in Mr Lynn's words, "flirting" with a work colleague called Aimee O'Shaughnessy. On March 8, Mr Slotsaa told Mr Lynn 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 swapped numbers. Throughout January 2026, Mr Slotsaa and Ms O'Shaughnessy met up for lunch on several occasions. Mr Slotsaa told Ms O'Shaughnessy that things were not great at home, and he told her he liked her, the prosecution said. She said she did not want to complicate things by starting a relationship with him, and according to her, he was fine with this, Mr Robinson added.
In the week of March 9 to 13, before 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.
Post-Mortem and Psychiatric Evidence
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 14 separate sharp force injuries, including 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 to prove diminished responsibility, the defence must establish that each of 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; that her abnormality arose from a recognised medical condition; that her abnormality substantially impaired her ability to understand the nature of her conduct, form a rational judgment, or exercise self-control; and that her abnormality caused, or was a significant contributory factor in causing, her to kill Mr Slotsaa.
Psychiatrist Dr Penelope Brown, instructed by the defence, formed the view that at the time of the killing, Cierpka was suffering from an episode of severe depression with marked suicidal tendencies, representing an abnormality of mental functioning from a recognised medical condition. In Dr Brown's opinion, the depressive episode impaired her abilities to form a rational judgment and exercise self-control, and as a result, the defence of diminished responsibility is available to Cierpka, the prosecution said.
The prosecution instructed another psychiatrist, Dr Shamir Patel, who concluded that Cierpka 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, he did not accept that it substantially impaired her ability to form a rational judgment or exercise self-control. Dr Patel also disagreed that her depression provided an explanation for her conduct; in his 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 relationship and her use of alcohol.
The trial continues at the Old Bailey.
