Chain of custody is the ability to say who held material at every point between its arrival and its disposal. It is a records property, not a security one: a locked cupboard with no log has physical control and no custody record at all.
It breaks at four predictable points, and each has a control that costs almost nothing.
Break one: between the courier and the shelf
Material is signed for by whoever is at the door and then sits somewhere until someone qualified puts it away. That interval is frequently undocumented, and it is also where a temperature question becomes unanswerable.
The control is a receipt note completed at the point of arrival rather than at the point of storage, which receiving and inspecting a shipment covers.
Break two: the vial that was moved but not logged
Someone takes a vial from the tray to a bench and brings it back. Nothing was used, so nothing was recorded, and the storage log now says the vial sat at a controlled temperature for an afternoon it spent on a bench.
The control is logging movement rather than only consumption. A line that records out and back with a name is sufficient.
| Point | What usually goes missing | Smallest control that holds it |
|---|---|---|
| Arrival to storage | Elapsed time and condition | Receipt note signed at the door |
| Storage to bench | That the vial left at all | Movement log, not just usage |
| Between people | Who had it when | Named handover line |
| Removal from inventory | That it left, and how | Disposal record with a witness |
Four breaks, four controls. None requires a system.
Break three: the informal handover
One person is away and another continues the work. Custody transferred and nothing records it. This is the break that matters most if anything is questioned later, because it is the point at which the record stops naming a responsible individual.
The control is a line in the log with both names. It takes seconds and it is the difference between a chain and a collection of unrelated entries.
Break four: disposal
Material leaves inventory and the record simply stops. An unexplained disappearance from a log is worse than no log, because it invites the question it cannot answer. Disposal and waste handling covers the mechanics; the custody point is narrower, which is that removal is an event and needs an entry like any other.
What a workable log looks like
One row per event, with the lot number running through every row so the chain can be reconstructed for a given lot rather than read chronologically. Date, lot, event, quantity, person, and a second name where custody changed hands. Six columns on paper is enough; the discipline is what matters, not the medium.
The lot number is the field that makes it reconstructable, which is the same argument as in records to keep.
What a custody record is actually for
Not for catching anyone. Its value is almost entirely in answering a question later, calmly, with a document rather than a recollection. The questions it answers are narrow and predictable: which lot was used, by whom, when, and under what conditions it had been held until then.
A practice that can answer those four from a log is in a completely different position from one that cannot, and the gap between them is a few seconds per event rather than a system.
Why the log should be lot-indexed
Because the question is always asked about a lot, never about a date. A chronological log forces a reader to scan the whole thing to reconstruct one material history; a log that can be filtered by lot answers the question directly.
On paper, that means the lot number in every row rather than in a header. In a spreadsheet it means a column rather than a tab per month. The structure is what makes the record usable, and it costs nothing to get right at the start and a great deal to retrofit.
Where separation matters
In a practice that also does non-research work, custody records are what demonstrate that research material stayed inside the research programme. Physical separation without a record shows intent; a record without separation shows nothing. Both are needed, and the record is the half that is visible to anyone looking afterwards.
For how this fits with everything else that happens to a vial between delivery and use, peptide storage and handling for clinics covers the full picture.