The coroner's inquest that has to survive Q-Day

The Coroners and Justice Act 2009 gives the senior coroner the power to open an inquest where the cause of death is unknown, violent, or in custody. Most inquests open within months of the death. A meaningful minority open years later, when new evidence comes to light, when a public inquiry into a wider failure reopens individual cases, or when the medical examiner refers a historical case for review. Hillsborough opened twenty-seven years after the event. The Infected Blood Inquiry reported on transfusions made forty years earlier. The Post Office Horizon Inquiry reviewed records two decades after the convictions.

A record entering coroner's evidence has to be the record produced at the time of the act, and it has to verify when the court asks.

That is the problem post-quantum cryptography is being moved into UK practice to solve.

What Q-Day actually does to a 2026 record

The NCSC published its post-quantum migration roadmap in 2024, with the strategic milestones set at 2031 (key government and critical national infrastructure systems migrated) and 2035 (all systems migrated). The NSA, CISA, and NIST have stated that harvest-now-decrypt-later is already operational: an adversary intercepts ciphertext today and waits for the cryptographically relevant quantum computer to break it later. The G7 has put post-quantum cryptography on its cyber-security agenda.

Q-Day, in operational practice, is the day on which the classical signatures on records produced today are forgeable. The exact date is contested. The structural certainty is that any record whose evidential weight depends on a classical signature has a fixed shelf life.

A 2026 audit record signed under ECDSA or RSA, presented in a coroner's court in 2036, is a record whose signature the defence can credibly question.

What the coroner needs the record to do

The coroner needs the record to satisfy three properties.

First, the record has to attribute the act to the actor. The clinician who issued the prescription. The custody officer who released the cell door. The transport controller who set the signal. The signature has to bind the act to a hardware-attested identity that the court can verify.

Second, the record has to verify against a public key the court trusts now, ten years after the act. The verification has to be possible without trusting the vendor of the original system, because the vendor may not exist by then, may have been acquired, may have been compromised, or may have changed its key custody arrangement.

Third, the record has to retain its evidential weight under cross-examination. The defence will probe every link in the chain. A signature scheme that a competent quantum adversary could break is a signature scheme the defence will probe successfully.

The substrate the inquest can read

Mickai signs every action record under FIPS 204 ML-DSA-65 at the moment of generation. ML-DSA-65 is the NIST-standardised post-quantum signature scheme the NCSC migration roadmap names as the target. The signing key for a deployment is bound to TPM 2.0 hardware held by the operator. The verification key is published. The verification step is browser-resident WebAssembly, performed offline if needed, against the operator's published key.

A 2026 record signed under ML-DSA-65 and stored in the Mickai Audit Ledger is a record the coroner in 2036 can verify with the same arithmetic that verified it in 2026. The key does not weaken. The signature does not become forgeable. The defence cannot credibly question the cryptographic binding.

The actor identity is bound under Mickai's hardware-attested identity primitive, the audit record under the Open Audit Record. Both are filed at the UK IPO under the Mickai portfolio.

Two scenarios the bench can recognise

A custody officer at a category-A facility uses an in-cell management system to make a release-from-observation decision. Eleven years later, a public inquiry into custodial deaths reopens the case. The Audit Ledger contains the action record: the decision, the prompts the model presented, the officer's signed acceptance, the hardware key under which the record was sealed, the time. The defence cross-examines the signature scheme. The expert witness verifies the ML-DSA-65 signature against the published key. The chain holds.

A clinical decision support system at an acute trust suggests an out-of-policy prescription, and the prescribing doctor accepts. Eight years later, the medical examiner refers the case to the coroner. The Audit Ledger holds the prescription record, the policy gate the action passed, the quorum margin, the doctor's signed acceptance, and the inverse-action chain that the trust used to retract the prescription at the time. The coroner verifies the record. The medical examiner closes the referral.

Policy alignment, not policy promises

The NCSC Post-Quantum Cryptography Migration page identifies the specific failure mode this article addresses: classical signatures on long-lived records become contested as Q-Day approaches. The Ministry of Justice's open justice principle assumes that records before the court are records the court can verify. The Coroners' Society's training materials assume that documentary evidence retains its evidential weight. The G7 communique on quantum-safe cryptography names the same migration deadline the NCSC has set.

A coroner's inquest that opens in 2036 against a 2026 record needs the record to have been signed under the scheme that survives the transition. That scheme is ML-DSA-65. The substrate that signs under it from inception is Mickai. The filings are on the public register.

What the trust, the custodial facility, and the transport operator should do

The structural test is straightforward. The audit records produced now have to be signed under the post-quantum scheme that the NCSC names, against a key the operator controls, with a verification path that does not depend on the vendor still existing in 2036. The Mickai Sovereign Intelligence Operating System provides each property as a primitive, filed at the UK IPO, available now.

The Mickai SIOS is the operating system. The coroner reads the record produced in 2026 and the signature still verifies. That is what post-quantum migration in the UK is actually for.