The Nuance Between Forensic Probabilities and Possibilities – Paediatric Gonorrhoea and Fomite Transmission – [2025] Fam Law 1445

We are pleased to share a new publication in Family Law Journal by Children and CoP barrister, Avaia Williams. In his latest article for Family Law Journal, Avi examines a significant issue, how courts should treat theoretical scientific possibilities when applying the balance of probabilities. Considering the Court of Appeal’s recent judgment in Re F and another (Fact Finding: Gonorrhoea) [2025] EWCA Civ 340, the article explores why the elevation of “fomite transmission” from a bare possibility into a determinative alternative, risks distorting fact-finding in cases involving paediatric sexually transmitted infections.

Avi reflects on what fomite transmission actually is and why it has acquired such prominence in recent litigation, before analysing how expert evidence framed in non-binary scientific terms can be misunderstood within a legal system that requires binary conclusions. He discusses the Court of Appeal’s clarification of Re A, B and C, dispelling the idea that it provides a prescriptive test, and explains why a mere theoretical mechanism should not be mistaken for a probable route of transmission, particularly where the medical consensus overwhelmingly points in another direction.

In concluding his piece, Avi notes:

“It is clear, since Re A, B and C, that the evidence of an almost exclusively sexually transmitted infection not being determinative of sexual contact has been wrongly inferred into a starting point or a significant hurdle which needs to be jumped. This has led to the factors ‘pointing the other way’ noted in Re A, B and C, being seen as such a checklist or determinative of the case (which we now know from Baker LJ’s own words are not such general checklist)

[…]

Re A, B and C was never a mandate to discount expert consensus whenever a fanciful alternative can be imagined; it was a reminder not to convict on science alone without canvassing the wider evidence. Re F and B restores the missing half of that equation: the wider canvas does not licence a court to simply discount what the science says is overwhelmingly likely. Nor does it sanction a ‘tick-box’ defence drawn from someone else’s litigation strategy.”

Avaia’s piece can be accessed here for those with a subscription to LexisNexis or in the December copy of Family Law Journal.