Chain of Custody for Lab Samples: Procedure, Form & Examples

Chain of custody (CoC) is the documented, unbroken record of who collected, handled, transferred, stored, analysed and disposed of a sample, and when. It proves that the sample tested is the same one that was collected, and that nobody had the opportunity to tamper with it along the way.

Every lab tracks samples, but a chain of custody goes further: every hand-off is signed, every seal recorded and every gap explained. When a result may end up before a regulator or a court, the custody record can matter as much as the result.

When is chain of custody required?

Chain of custody is needed whenever the identity or integrity of a sample may be challenged. Common situations include:

• Forensic and toxicology: samples linked to criminal or coroner investigations.
• Workplace drug testing: regulated programmes often prescribe a custody and control form.
• Environmental and regulatory compliance: effluent, drinking water or soil tested against a permit or limit.
• Legal disputes: contested shipments, insurance claims or product liability.
• Food fraud investigations: authenticity testing of honey, olive oil, saffron or meat species.
• Clinical trials: specimens shipped from sites to central labs.

Requirements vary by authority and programme in the UAE and India, so confirm what the regulator or customer expects before sampling starts.

Chain of custody vs routine sample tracking

What a chain of custody form must record

Formats vary, but a robust CoC form or electronic record captures:

• Unique sample ID matching the container label
• Collector, signature, date and time of collection
• Sampling location and method
• Sample type, container, preservative and number of containers
• Condition and temperature at collection and receipt
• Tamper-evident seal numbers and their condition
• Every transfer: names, signatures, date and time
• Storage location and conditions
• Analyses requested and who opened the sample
• Retention period and disposal or return

The form is a controlled record like any other. Entries must be attributable, legible, contemporaneous, original and accurate, the core of ALCOA+.

Sample chain of custody procedure, step by step

1. Plan: agree methods, containers, preservatives, holding times and the CoC form with the customer.
2. Collect: sample by the specified method, label immediately, and record collector, time and location.
3. Seal: apply tamper-evident seals, record the seal numbers and sign.
4. Transfer: at every hand-off, both parties sign, date and time the form, which travels with the samples.
5. Transport: maintain the temperature the method requires and keep any temperature log.
6. Receive: check seals, labels, temperature, containers and holding time against the form, recording any deviation before proceeding.
7. Store: use secure, access-controlled storage and log the location.
8. Analyse: record each removal from storage and who broke the seal.
9. Retain and dispose: keep samples and records for the required period, then dispose of or return them with a signed record.

What to record at each stage

How ISO/IEC 17025:2017 applies

For testing labs, chain of custody builds on clause 7.4 of ISO/IEC 17025:2017, handling of test or calibration items. It requires a procedure for transport, receipt, handling, protection, storage, retention and disposal or return, and unambiguous identification of items while the lab is responsible for them.

Clause 7.4 also requires deviations from specified conditions to be recorded on receipt. Where an item's suitability is in doubt, the lab consults the customer before proceeding and records the outcome. If the customer wants testing anyway, the report must include a disclaimer indicating which results may be affected. Clauses 7.3 (sampling) and 7.5 (technical records) also apply.

Digital chain of custody: LIMS and barcodes

Many labs now run chain of custody in a LIMS, scanning barcoded containers at each hand-off.

• Pros: automatic time stamps, fewer transcription errors, a searchable audit trail and real-time location of every sample.
• Cons: the system needs validation, unique logins and audit trail review; field and courier steps often remain on paper; and downtime needs a tested paper fallback.

Worked example: a broken seal on a Ras Al Khaimah water sample

An industrial facility in Ras Al Khaimah sends treated wastewater samples to an accredited lab for a regulatory compliance test. A field technician seals each bottle and the cooler with numbered seals and signs the CoC form; a courier delivers the same afternoon.

At receipt, the cooler seal is intact but one bottle seal is torn. Temperature is within range and nothing is leaking. The lab:

1. Records the deviation on the CoC form and receipt record, with photographs, before anything else.
2. Quarantines the affected bottle and processes the rest as normal.
3. Contacts the customer the same day, explains that the integrity of that bottle cannot be confirmed, and records the conversation.
4. Recommends resampling, because the result may support a regulatory submission.
5. If the customer still requests testing, adds a report statement that the seal was broken on receipt and results may be affected.
6. Raises a nonconformity to investigate with the sampling team and courier.

The seal had been applied to a wet bottle neck and lifted in transit. The facility changed seal type and now dries bottles before sealing, and resampling produced a clean custody record. Confirm reporting and resampling expectations with the relevant authority.

Common mistakes

• Leaving gaps in the transfer record, such as samples sitting unsigned in a vehicle or reception area.
• Recording seal numbers at collection but not checking them at receipt.
• Pre-filling times or signing on someone else's behalf.
• Overwriting entries instead of a single-line correction with initials and date.
• Opening a sample before recording its receipt condition.
• Discarding samples before the agreed or required retention period ends.

Key takeaway: A chain of custody is only as strong as its weakest hand-off. Record every person, time, seal and condition from collection to disposal, check seals at receipt, and consult the customer before testing anything that arrives compromised.

Frequently Asked Questions

What is a chain of custody form?

A chain of custody form is the paper or electronic document that travels with a sample and records its identity and every change of possession. It typically includes the sample ID, collector, collection date and time, location, seal numbers and condition, plus the signature, date and time of each person who releases or receives the sample, through to analysis and disposal.

What happens if the chain of custody is broken?

A break, such as a missing signature, an unexplained time gap or a damaged seal, means the lab cannot fully prove the sample was not altered. For routine work it may be a documented deviation. For forensic, legal or regulatory samples, it can make the result unusable as evidence. The lab should record the issue, inform the customer and consider resampling.

Is chain of custody required for ISO/IEC 17025 accreditation?

ISO/IEC 17025:2017 does not require a formal chain of custody for every sample. Clause 7.4 does require procedures for transport, receipt, handling, storage, retention and disposal, unique identification of items and recording of deviations on receipt. Labs handling legal or regulatory samples usually build a full CoC procedure on that foundation. Confirm specific expectations with your accreditation body.

Who signs a chain of custody form?

Everyone who takes possession of the sample: usually the collector, any courier, the lab's receiving officer, the sample custodian and the analyst. At each transfer, both the person releasing and the person receiving sign, with the date and time, so no period of custody is left unaccounted for.

Next steps

Defensible results start with disciplined records. Our Good Documentation Practices and Data Integrity Essentials course builds those habits, and ISO/IEC 17025 Advanced Laboratory Competence and Accreditation goes deeper into sample handling, technical records and accreditation.

Related reading: pre-analytical errors: a lab checklist, ALCOA+ data integrity explained and laboratory biosafety vs biosecurity. For help choosing a course, speak to a counsellor.