A worked example of hash-chained custody authentication, tier-scoped access per custodian, and structural Brady disclosure in the legal evidence custody variant of the ABT methodology family.
The ABT-L variant applies the foundational envelope-tier architecture to physical evidence custody, with a five-hand criminal case chain as the canonical scenario. The variant-specific architectural elements are: per-custodian tier keys, such that each hand in the custody chain — collecting officer, forensic lab, prosecution, defense, court — holds a cryptographic key that decrypts only the tier projection authored for that custodian's institutional function; hash-chained transfer events, in which each handoff produces a registry entry that extends the chain, making any unrecorded transfer immediately detectable; and structural Brady disclosure, in which the defense tier is constructed at collection time and addressed directly to defense counsel's key — sealed against modification by the prosecution from the moment of collection. This memorandum follows evidence item EV-2024-0441 across five custody hands, identifying the legal significance of each architectural property.
At the moment of collection, the ABT-L envelope is constructed with five independent tier projections: one for each hand in the anticipated custody chain. Each tier is sealed to the key of its intended custodian. The collection event is recorded in the registry as h_0.
| Custodian | Tier access | Function |
|---|---|---|
Det. Ines Guerrero Collecting officer · first hand | Officer tier key — collection circumstances, scene notes | Collects item; constructs envelope; signs at scene |
Regional Forensic Laboratory Analysis custodian · second hand | Lab tier key — analysis instructions, findings | Receives item; decrypts lab tier; performs and records analysis |
District Attorney's Office Prosecution · third hand | Prosecution tier key — evidentiary summary, case reference | Receives item; reviews prosecution tier; manages trial preparation |
Defense Counsel Defense · fourth hand | Defense tier key — same evidentiary content as prosecution tier; sealed at collection | Receives tier via registry direct; cannot have been modified by prosecution |
Trial Court Court · fifth hand | Court tier key — chain summary; all prior hash chain entries authenticated | Receives item; verifies complete chain; rules on admissibility |
The defense tier was constructed at collection time by Detective Guerrero's device and sealed to the defense counsel key. The prosecution held the evidence between h_1 (lab) and h_2 (prosecution) — but the defense tier remained sealed to the prosecution's key throughout. Defense counsel receives the tier as it was recorded at h_0.
Traditional Brady disclosure requires the prosecution to identify, evaluate, and voluntarily produce material exculpatory evidence. This creates a structural accountability gap: the prosecution holds a monopoly over the initial identification of what is Brady material. ABT-L addresses this gap at the architecture level. The defense tier is constructed at collection time from the same underlying evidence record as the prosecution tier. Its contents are determined by the evidence record — not by the prosecution's disclosure decision.
The prosecution cannot suppress Brady material by omitting it from the defense tier — because the defense tier is not authored by the prosecution. It is authored at the scene by the collecting officer's envelope construction, addressed to the defense counsel key. Prosecution is not in the authoring path for the defense tier.
At trial, the court receives EV-2024-0441 with the complete hash chain. Each entry in the chain is verified against its predecessor. A single unrecorded transfer or alteration produces a verification failure.
| Custodian | Holds | Cannot produce | Legal significance |
|---|---|---|---|
| Det. Guerrero | Officer tier: scene notes, collection circumstances | Lab findings, prosecution notes, defense tier | Subpoena for "all evidence records" yields officer tier only; cannot compel production of tiers not held |
| Forensic Lab | Lab tier: analysis findings, DNA/fingerprint results | Collection scene notes, prosecution notes | Lab cannot produce collection circumstances from officer tier — it does not hold them |
| Prosecution | Prosecution tier: evidentiary summary, case reference | Defense tier (sealed to defense key at collection) | Prosecution cannot produce the defense tier; it was never addressable to prosecution key |
| Defense Counsel | Defense tier: evidentiary summary (same content as prosecution tier, sealed at collection) | Prosecution's work product in prosecution tier | Defense demonstrates receipt of unmodified tier from registry chain |
| Registry | Hash chain entries: transfer timestamps, chain hashes — no case content | Any tier content — registry holds only hash proofs | Registry subpoena yields tamper-evident log of transfers; no PII, no evidentiary content |