Context
The Letby trial in 2022–2023 heard witness evidence on events from 2015–2016 — a six-to-eight-year delay. The retrial in 2024 heard evidence on the Child K event from 2016 — an eight-year delay. The Thirlwall Inquiry in 2024–2026 has heard evidence on events from 2015–2017 — a nine-to-ten-year delay. Cognitive-psychology literature has specific findings about witness testimony reliability at these delay ranges.
The five principal memory-science findings
- Memories are reconstructive, not recording.
- Accuracy declines with time for specific details.
- Repeated retelling modifies memory.
- External information integrates with memory.
- Confidence and accuracy are weakly correlated over long delays.
Application to Letby witness testimony
Between the 2015–2016 events and the 2022–2023 trial, witnesses had: participated in internal reviews; been interviewed by Cheshire Police multiple times; consulted legal representatives; read press coverage; prepared witness statements; conferred with each other. Each of these is a source of post-event information integration under memory-science terms. The testimony at trial was not raw 2015–2016 recollection; it was substantially reconstructed recollection after years of intermediate information exposure.
Contemporaneous records are more reliable
The memory-science reliability hierarchy places contemporaneous records (Datix logs, clinical notes, email, meeting minutes) above long-delay witness testimony. The Letby case has a substantial contemporaneous record, now largely placed in public evidence by the Thirlwall Inquiry. On the reliability hierarchy, those contemporaneous records should carry more weight than the 2022–2023 trial testimony where the two conflict.
What UK courts already know
UK criminal courts have developed memory-science awareness through historic-abuse cases. Judicial direction on long-delay testimony in historic-abuse cases specifically addresses the reliability limits. The Letby trial directions did not systematically invoke equivalent memory-science framing — a specific conviction-safety consideration for CCRC review.
Read alongside
The seven-year-delay problem, Child K ET-tube detail, Evidence: witness memory long-delay, Evidence: contemporaneous medical notes.