Rought draft: From Deepfakes to Machine-Mediated Reality: Epistemic Decoupling and the Duty of Evidential Grounding in UK Public Law

This paper argues that UK public law contains no sufficiently developed principle governing decisions based on machine‑mediated states of affairs: situations in which an automated system does not merely observe or classify the factual basis of a decision, but materially alters that factual basis before supplying the evidence of it. As AI systems increasingly act in the physical world—inspecting, adjusting, and maintaining the infrastructure that later decisions depend on—the system that changes a state of affairs often becomes the primary source of evidence about it, closing an evidential loop that existing doctrine was not built to open. The paper distinguishes three objects of machine‑mediated governance concern: machine‑generated representations, machine‑generated actions, and machine‑generated or machine‑modified states of affairs. UK public law addresses the first two through evidential and product‑safety doctrine, but not the third. Existing doctrines of procedural fairness, rationality, disclosure, and evidential reliability—including the presumption that a computer system was operating correctly, and the duty of candour in judicial review—provide partial safeguards, but they do not consistently require preservation of a baseline state, an intervention history, or an independent means of verification. Drawing on the Post Office Horizon litigation and recent judicial commentary on automated decision‑making, the paper proposes a duty of evidential grounding: a requirement that public authorities take reasonable and proportionate steps to preserve the records needed to reconstruct the factual basis of a materially consequential decision. It develops a graduated machine‑mediated grounding test for applying that duty, proposes an adverse‑inference consequence for unjustified failures of preservation, and offers a model statutory clause as a possible codification.