Jurors at Lincoln Crown Court have heard further evidence in the case of a 13-year-old girl accused of murdering a woman during a knife attack earlier this year. The defendant, who cannot be identified because of her age, is charged with the killing of Marta Bednarczyk, who died in March after sustaining more than 140 sharp-force injuries, the court was told.
During the trial, a consultant psychologist described meeting the teenager around eight weeks after the incident. According to the expert’s testimony, the girl appeared at ease during the assessment and engaged openly in conversation, at times giving the impression that she enjoyed discussing the events surrounding the death.
The court heard that the girl told the psychologist she had experienced a voice instructing her to harm 43 years old, Ms Bednarczyk. The evidence was presented as part of a broader examination of the defendant’s mental state following the alleged attack. She accepts she committed the crime though is claiming diminished responsibility. The jury was told that the girl described the moments leading up to the knife attack during her assessment with Dr Tim Diggle, saying it felt as though her body was acting without her control.
Following the stabbing, the court heard, the teenager told the psychologist she struggled to accept what had happened and did not want to believe she was responsible. As a result, she admitted giving false information to police officers in the immediate aftermath.
Jurors were reminded that expert psychological evidence is intended to assist the court in understanding complex behavioural and mental health issues, particularly when young defendants are involved. The question of criminal responsibility remains a matter for the jury to decide.
Expert witness and psychologist, Dr Diggle, assessed the girl for more than three hours in May 2025: “She was very personable. She communicated very well…very effectively She was able to give quite elaborate descriptions and she seemed to enjoy taking part in the process, enjoy having an audience,” he said.
Asked by counsel for the Crown whether that was unusual, the expert witness replied: “Generally speaking when I assess young people they tend to be more truculent, are often notably anxious and struggle to communicate and take part in the interview.
“Her (the defendant’s) communication skills seemed very good. Both in regard of her spoken word and also non-verbal communication including things like eye contact.”
Jurors also heard details of digital evidence linked to the defendant, including WhatsApp messages and internet searches. Among them was a Google query asking: “How do I know if I’ve got a mental illness?”
The court was reminded of earlier medical evidence presented last week, when a Home Office pathologist described examining Ms Bednarczyk’s body. The examination identified multiple wounds to the face, neck and back, as well as defensive-type injuries to the arms and hands.
During cross-examination by defence counsel, Dr Diggle agreed it was possible the girl had entered a dissociative state at the time of the killing. He also accepted that such a state could have affected her ability to properly recall events surrounding the incident.
Expert Witnesses Involved
1. Dr Tim Diggle
Discipline: Clinical / Forensic Psychology
Role in the case:
• Conducted a psychological assessment of the defendant approximately eight weeks after the alleged killing
• Gave evidence about the girl’s mental state, behaviour, and presentation during the assessment
Key areas of testimony:
• The defendant’s account of events leading up to the stabbing
• Her description of feeling as though her body “moved on its own”
• Post-incident behaviour, including giving false information to police
• Observations of her composure, mood, and responsiveness
• The possibility that she may have entered a dissociative state at the time of the killing
• Whether such a state could affect memory and recall
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2. Home Office Pathologist (Name not reported)
Discipline: Forensic Pathology
Role in the case:
• Conducted the post-mortem examination of the deceased, Marta Bednarczyk
Key areas of testimony:
• Cause of death
• Number and location of sharp-force injuries
• Wounds to the face, neck, and back
• Injuries to the arms and hands, consistent with defensive wounds
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