Changing Caregiver Histories as Circumstantial Evidence (and the Permissible Judicial “Distillation” of Complex Medical Proof)

1. Introduction

In AA v His Majesty’s Advocate [2026] HCJAC 31 (Appeal Court, High Court of Justiciary; Opinion of the Court delivered by the Lord Justice General, sitting with Lady Carmichael), the appellant challenged his conviction for attempting to murder a young child by shaking and/or otherwise inflicting head trauma.

The prosecution case was circumstantial and rested heavily on (i) exclusion of other carers, (ii) the appellant’s varying accounts of incidents said to have happened while the child was in his care, and (iii) expert medical evidence supporting abusive head trauma by shaking, on more than one occasion.

The appeal focused on whether there was unfairness in: (a) the scope and use of evidence from a forensic paediatrician (Dr Forrester) said to have strayed beyond expertise and then relied upon in the Crown address; and (b) alleged imbalance in the trial judge’s charge through a summary of technical medical evidence.

2. Summary of the Judgment

The court refused the appeal. It held, in essence, that:

  • Any brief excursion by Dr Forrester into timing of immunisation symptoms was transparently flagged as beyond her expertise and was not relied upon thereafter; no miscarriage of justice arose.
  • Where Dr Forrester said a topic was beyond her expertise (bridging veins), she gave no evidence on it; the relevant testimony therefore did not found unfairness.
  • Dr Forrester’s “red flags” evidence about changing histories, delay in disclosure, and inconsistency with development/medical findings was not inadmissible expert opinion; it was a description of professional practice and investigative triggers.
  • The Crown was entitled to invite the jury to treat the appellant’s delay, lies, and shifting accounts as circumstantial evidence, consistent with Bovill HM Advocate [2003] SCCR 182.
  • Although the trial judge gave certain directions favourable to the appellant that were incorrect (notably downplaying the circumstantial significance of lies and directing parts of Dr Forrester’s evidence to be disregarded), these did not produce a miscarriage of justice against the appellant.
  • The judge’s approach to summarising complex medical evidence was within discretion; read fairly and in context, the charge was not imbalanced.

3. Analysis

3.1 Precedents Cited

(a) Expert evidence: admissibility and scope

The court noted that expert evidence was plainly required and referenced Christie v HM Advocate [2024] HCJAC 52, 2025 SCCR 365 as a recent discussion of criteria for admission. Although the appeal did not turn on a fresh restatement of admissibility tests, the decision reinforces a practical point: the critical question on appeal is not whether an expert uttered something arguable at the margins, but whether the trial process (including judicial intervention and how the Crown used the evidence) produced a miscarriage of justice.

(b) Circumstantial significance of lies and delayed disclosure

The court expressly approved the Crown’s invitation to treat the appellant’s delayed disclosure and admitted lying as part of the “complete picture” and therefore as circumstantial evidence, citing Bovill HM Advocate [2003] SCCR 182. The court treated the appellant’s shifting accounts—not as mere credibility material with no further consequence—but as capable of supporting an inference that he was attempting to “fool everyone into believing” an innocent explanation for injuries.

This sits in tension with (and explains why the court criticised) the trial judge’s suggestion that rejected evidence must simply be put out of mind and cannot assist the Crown. The Appeal Court’s emphasis aligns with the orthodox distinction between:

  • rejecting a witness’s account (which does not, by itself, prove the opposite), and
  • proven lying/delay/contrivance as an independent evidential circumstance capable of supporting inference of consciousness of guilt.

(c) The judge’s role in handling technical evidence and alleged imbalance

On the charge, the court drew on a line of authority about when and how a judge should assist a jury with complex proof:

  • Liehne v HM Advocate 2011 SCCR 419, [2011] HCJAC 51: it can be a misdirection to leave technical evidence “at large”.
  • Hainey v HM Advocate 2014 JC 33, [2013] HCJAC 47: similarly recognises the need for appropriate guidance.
  • Geddes v HM Advocate 2015 JC 229, [2015] HCJAC 10: emphasises there is generally no requirement to rehearse or summarise evidence; the duty is a coherent “route to verdict”, and at most a “succinct, balanced review” of central matters. The court also cited Younas v HM Advocate 2014 SCCR 628 (as quoted in Geddes).
  • Sim v HM Advocate 2016 JC 174, [2016] HCJAC 48: restates appellate approach to alleged misdirections and imbalance, including that directions must be read as a whole and in the context of the oral tradition; imbalance must go to the tenor of the charge (with reference to Beck v HM Advocate, Snowden v HM Advocate 2014 SCCR 663, Scott v HM Advocate 1946 JC 90, Keaney v HM Advocate, and Withers v HM Advocate 1947 JC 109).

Applying these principles, the court held the judge was entitled—indeed, might have been criticised if he had not—to distil the medical evidence, which was central, technical, and not easy to follow. The charge sufficiently reflected defence points; no substantial imbalance was demonstrated.

3.2 Legal Reasoning

(a) “Beyond expertise” moments: what matters on appeal

The appellant’s complaint focused on three areas of Dr Forrester’s testimony:

  • Immunisation symptoms timing: Dr Forrester herself flagged that timing was “probably not my area of expertise”, and the trial judge immediately intervened in front of the jury instructing her not to stray beyond expertise. The topic then ceased and was not relied on by the Crown. The Appeal Court treated this as a self-contained incident with no prejudicial afterlife.
  • Bridging veins: when asked directly, Dr Forrester said it was beyond her expertise; thus she gave no evidence on the point. The court rejected any suggestion that earlier head-trauma evidence was necessarily outwith her competence, given her forensic paediatric role.
  • Changing histories/delay/inconsistency: the court rejected the characterisation of this as inadmissible expert opinion. It was framed as routine professional practice—factors that may trigger inquiry—rather than a specialised “branch of knowledge” usurping the jury.

(b) Crown address: permissible use of “red flags” and the jury’s role

The Crown’s speech invited the jury to consider whether three “indicators” described by Dr Forrester were present on the evidence. The Appeal Court held this was legitimate: the jury were entitled to consider delayed disclosure, shifting accounts, and developmental inconsistency as circumstantial factors, and the Advocate Depute expressly reminded the jury that assessment was for them “and you alone”.

The court’s reasoning is practical: in a circumstantial abusive-head-trauma case, the chain of inference may include not only medical conclusions, but also the caregiver’s conduct in responding to and accounting for events.

(c) Misdirections favourable to the appellant and the “no miscarriage” conclusion

A striking feature of the opinion is the court’s identification of errors in the charge that benefited the appellant:

  • The judge suggested that asking “why the accused is lying” was not an approach the jury should take, and implied lying could not support the Crown case. The Appeal Court held this “misses the point”: proven lying/delay can itself be circumstantial evidence (Bovill).
  • The judge directed the jury that parts of Dr Forrester’s evidence were “inadmissible in law” and should be disregarded. The Appeal Court considered that direction wrong (both as to intracranial injury discussion and as to “red flags”).

Those errors did not assist the appellant on appeal because they did not create unfairness against him; if anything they were protective. The court therefore found no miscarriage of justice arising from either the evidence complained of or its treatment in speeches/charge.

(d) Sifting and specification of grounds

Although not the ratio of refusal, the court criticised the way leave was granted at sift: it described the grant as “somewhat obtuse” and stated that grounds should have been specified in terms of section 107(7) of the Criminal Procedure (Scotland) Act 1995. The practical point is procedural discipline: unclear leave can distort the focus of appeal submissions and complicate identification of what is truly in issue.

3.3 Impact

  • Child-abuse and abusive head trauma prosecutions: the decision supports a structured circumstantial approach where the caregiver’s delayed disclosure, inconsistency, and admitted lying can be deployed as part of the inferential case, alongside medical conclusions.
  • Expert evidence management: it endorses active judicial control where a witness signals limits of expertise, but indicates that a brief, transparently disclaimed answer—unrelied upon—will rarely justify appellate intervention.
  • Directions on lies: the opinion underscores that trial directions should not inadvertently neutralise legitimate circumstantial reasoning about lies/delay; while “rejection does not prove the opposite” remains true, proven fabrication can still be evidence of consciousness of guilt.
  • Summaries of complex expert proof: reaffirming Liehne, Hainey and Geddes, the court signals that careful distillation may be appropriate where technical evidence is central and difficult, provided it is balanced and leaves ultimate evaluation to the jury.

4. Complex Concepts Simplified

  • Circumstantial case: the prosecution proves a set of facts (medical findings, opportunity, exclusion of others, inconsistent accounts) from which the jury may infer guilt, rather than relying on direct eyewitness evidence of the act.
  • Expert evidence “within/outwith expertise”: an expert may speak only within demonstrated specialised knowledge/experience. If they explicitly say something is beyond their expertise, the court will usually treat that as limiting what weight (or admissibility) the evidence can have—here, the key was that the jury heard the limitation and the point was not pursued.
  • Lies as evidence: a lie does not automatically prove guilt; but if the jury conclude a lie was told deliberately to mislead about a material issue, it can be treated as one circumstance supporting an inference of guilt (as part of a wider evidential picture).
  • “Imbalance” in a charge: an appeal will not succeed merely because the judge mentioned more Crown evidence than defence evidence. The imbalance must be substantial and affect the overall tenor of the directions when read as a whole and in context.
  • “Route to verdict”: directions that help the jury understand the legal tests and how to approach the issues; the judge need not recount all evidence but may summarise central technical matters to make the route workable.

5. Conclusion

[2026] HCJAC 31 confirms two practical propositions of continuing importance in Scottish criminal trials involving technical expert proof and circumstantial reasoning:

  • The Crown may legitimately rely on shifting or delayed caregiver histories and admitted lying as circumstantial evidence within the overall inferential case (with Bovill HM Advocate [2003] SCCR 182 providing the touchstone).
  • A trial judge may—and sometimes should—distil complex medical evidence for the jury, and appellate courts will be slow to find “imbalance” absent a substantial skew affecting the tenor of the charge (drawing on Geddes v HM Advocate 2015 JC 229, [2015] HCJAC 10 and related authority).

The appeal failed because the complained-of expert evidence either did not stray beyond expertise in any harmful way, or was not improperly exploited; and the judge’s charge, though containing errors favourable to the defence, did not create a miscarriage of justice against the appellant.