SECAI Core · phase 4 of 15 · noun

Chain of custody

Record of handling evidence from collection to presentation in court to disposal.

The Explain card

Plain English: Chain of custody is the documented record of who handled evidence, when and how, from collection through presentation in court to final disposal.
Example: After an AI system is suspected of being poisoned, investigators image the training data store and model checkpoints, hash them, and log every handoff so the findings hold up later.
Why it matters: AI incidents produce evidence too: datasets, weights, prompts, logs. Without an unbroken chain, you cannot prove what the model was when it misbehaved or who touched it.
Hook: Every handoff signed, or the evidence is just a story.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

The examiner attaches the seized drive to a write blocker, hashes the model checkpoint, and enters the SHA-256 in the chain of custody.

Why these words

chain Old French chaine, from Latin catena, a chain or fetter supplies the linked-links half, so the keeping is pictured as a series of hands rather than a single lock
of Old English of, from or away from the genitive hinge, so the chain belongs to the keeping rather than to iron
custody Latin custodia, a watching, from custos, guardian names the keeping, so the phrase claims a watch can be passed like a link

Where it came from

Origin: English legal collocation from Old French chaine (from Latin catena, a chain or fetter), Old English of, and Latin custodia (a watching, from custos, guardian)
Entered the language: 1950s
What changed: Chain had meant iron links, then any series of connected things, then a line of people who pass a charge. Custody had meant a watching, then the keeping of a person or a thing, then the legal hold a jailer or a clerk can name. Lawyers had long talked of a continuous possession; American evidence writing of the 1950s joined the two into this collocation, and digital forensics later asked the same trail of a disk image and a model checkpoint.

How it is spelled

Pattern: ai spells /eɪ/ in chain, a French leftover from chaine
Pattern: c before u stays /k/ in custody, as in custom
Pattern: Latin -ia becomes English -y in custody, as in memory
Breaks the pattern: the noun phrase stays three words; hyphens appear only when the stack modifies another noun
Breaks the pattern: chain keeps ai for a sound Latin catena never spelled that way
Breaks the pattern: custody looks as if the o might be long, but it is a schwa

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

Lineage and custody

Chain-of phrases

Custody family

Phase 4: Data Integrity, Governance, and Provenance

Once you know what data is, learn the principles that keep it trustworthy, traceable, and minimized throughout its lifecycle.