Lucy Letby, Dr. Dewi Evans And The 'Noxious Substance'

The host examines Dewi Evans's use of the term 'noxious substance' in court, showing he raised it as a differential diagnosis for Baby A but dismissed it, then inexplicably reintroduced it for Baby M even though the clinical presentations of potassium chloride poisoning and air embolism are entirely distinct. Using detailed comparison of ECG changes, imaging findings, and post-mortem indicators, the host argues the two conditions cannot be treated as interchangeable alternatives. The video also draws on journalist David Rose's UnHerd investigation revealing that Evans originally flagged ten suspicious incidents when Letby was not on duty—incidents quietly removed from the case. The host concludes that Evans's diagnostic process was not a genuine differential diagnosis but worked backwards from a presumption of guilt.

Last updated 2026-07-14

2 min read

Notable extracts

Extracts transcribed from the linked video, quoted under fair dealing for review and news reporting (CDPA 1988 s.30). Source links are being restored: these extracts were transcribed from the videos but the per-video URLs and timestamps were not recorded, so they cannot yet be checked against the recording. Treat them as reported rather than verified, and see our corrections policy if you believe one is wrong.

Dewi Evans (quoted from court transcript)

There is no basis to suggest potassium chloride had been used, was there? None at all as far as I know. None at all as far as I know. This is why we have spent the last few hours talking about air ambulances, which is what I did think occurred.

Topic: Evans cross-examined by Ben Myers on noxious substance for Baby A

David Rose (journalist, quoted from Talk TV interview)

What I published in UnHerd is evidence that when he first conducted an analysis and met the police over two days in October 2017, he identified 10 occasions when he thought suspicious occurrences had taken place when in fact it then transpired that Lucy Letby was not on duty.

Topic: David Rose on UnHerd investigation into Evans's original analysis

Reddit commenter (NHS professional, quoted by host)

A diagnostic process that works back from okay if someone wanted to kill this baby how would they have done it past potassium is gibberish. The serious concern here is the misrepresentation of diagnostic process that went unchallenged due to the absence of defence witnesses.

Topic: Reddit NHS professional on Evans's differential diagnosis methodology

Speaker 1 (host)

He decided that within 10 minutes of arriving at the police station for his first meeting with Cheshire Police in July 2017 and having a look at these notes over coffee I felt oh my god this baby's the victim of inflicted injury. So it took you 10 minutes to decide this baby had been put in harm's way.

Topic: On Evans's stated timeline for reaching his diagnosis

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