The retrial framework — Criminal Justice Act 2003 section 76
The double jeopardy rule — the common-law principle that an acquitted defendant cannot be tried again for the same offence — was substantially modified by Part 10 of the Criminal Justice Act 2003. Section 76 creates a statutory exception that allows the prosecution to apply to the Court of Appeal for an order quashing an acquittal and directing a new trial, where “new and compelling evidence” has emerged that was not available at the original trial.
The provision applies to a defined list of serious offences. Murder is the principal qualifying offence. Attempted murder also qualifies. The CJA 2003 Part 10 regime is therefore directly applicable to the Letby jury-disagreement counts, which were on attempted-murder and murder charges.
Two procedural conditions must both be satisfied before a retrial can be ordered: (1) the Court of Appeal must be satisfied that new evidence exists that is both “new” (not reasonably available at the original trial) and “compelling” (reliable, substantial, and highly probative); and (2) it must be in the interests of justice to order a retrial. The Attorney General must consent to the application.
What “new and compelling evidence” means
“New” evidence under section 78 of the CJA 2003 means evidence that was not adduced at the original proceedings, either because it did not exist at the time or because it was not reasonably practicable to adduce it. Post-conviction expert reports that were not available at trial would qualify as “new” on the straightforward ground that they did not exist when the jury deliberated.
“Compelling” evidence must satisfy a higher threshold: it must be reliable, substantial in weight, and such that, considered together with the other evidence in the case, it is highly probable that a reasonable jury would convict. This is the prosecution’s threshold for a retrial application. Note the asymmetry: where the prosecution seeks a retrial of an acquitted defendant, it must show that conviction is highly probable on the new evidence. Where the defence seeks a CCRC referral of a conviction, the threshold is lower: the CCRC must identify a real possibility that the conviction would not be upheld.
How this applies to the Letby jury-disagreement counts
The jury returned non-verdicts (hung jury) on counts relating to Babies H, J, N, and Q. A hung jury is not an acquittal. As a matter of English law, a hung jury leaves the defendant in jeopardy: the prosecution may apply to re-try the defendant on the same count without needing to satisfy the CJA 2003 Part 10 conditions. The double jeopardy reform is irrelevant to hung-jury counts because no acquittal occurred.
The practical position on the jury-disagreement counts is therefore as follows. The prosecution could seek a retrial on Babies H, J, N, and Q counts on the existing evidence, without needing to demonstrate new and compelling evidence. Whether it would be in the public interest to do so is a separate prosecutorial discretion question. In the current post-conviction context — where the defence is advancing a substantial body of new expert evidence for the CCRC — such a prosecution application would be highly unusual.
For the per-case analysis of the jury-disagreement counts, see: Baby H deep-dive, Baby J deep-dive, Baby N haemophilia differential, and Baby Q deep-dive.
The CCRC pathway versus the retrial pathway
The two pathways operate independently and address different questions. The CCRC pathway is a post-conviction review mechanism for defendants who have been convicted. It asks whether there is a real possibility that the conviction would not be upheld if referred back to the Court of Appeal. It is available to Letby on the 14 conviction counts.
The retrial pathway under CJA 2003 section 76 is a prosecution mechanism for defendants who have been acquitted of qualifying serious offences. It is not directly available to Letby as a defence tool; she cannot use it to seek a new trial on the jury-disagreement counts. However, the existence of the CJA 2003 framework is relevant context for understanding the procedural finality question: the jury-disagreement counts remain technically open to prosecution, which is part of the procedural backdrop against which the CCRC application sits.
What the Sumption analysis identifies
Lord Sumption’s public commentary on the Letby case addresses the conviction-safety question from the perspective of a former Supreme Court Justice. His analysis identifies the statistical and clinical reasoning at trial as the weakest elements of the prosecution case, and notes that the new expert material — particularly on the statistical cluster evidence and the clinical differentials for the haemorrhage-feature counts — is precisely the type of evidence that the Court of Appeal would need to evaluate on a CCRC referral.
Sumption’s analysis does not address the retrial framework specifically, but it is relevant to the “interests of justice” assessment that would apply to any retrial application on the jury-disagreement counts: if the clinical foundation of the original prosecution is materially undermined by new expert evidence, the interests of justice would not readily support a retrial of the non-conviction counts in advance of CCRC review of the conviction counts.