An important legal aspect of sampling and analysis is the 'chain of custody'. This is particularly the case when samples are collected on site and transferred to an analytical laboratory for testing. Results may be challenged in court if a clear chain of custody of the samples is not present.

This guidance note illustrates the concepts involved in securing a valid chain of custody for samples.


The essence of chains of custody is that the location and personnel responsible for test samples can be traced from the moment that the samples are taken to the time that the final results are reported to the client. This involves custody by the sampling team until the samples are relinquished, then transport by courier/etc. to the laboratory performing the analysis, and finally the chain of events within the laboratory leading to the reporting of the results.

There are three elements to consider:

1. Control of custody at site is normally achieved by a member of the sampling team being made responsible for the correct labeling and storage of samples. The samples, once taken, must be clearly identified and ideally sealed in such a way as to make tampering evident. Their storage must then be controlled and their storage environment be fit for purpose.

2. Transport via a courier normally involves the completion of shipping notes that include brief descriptions of the samples. Couriers normally have good records of dates/times of receipt and delivery, including names/signatures of personnel involved.

3. Once in the laboratory, the custody of samples is normally very well controlled, as many samples from many different customers must be tested and reported correctly. There should be little reason for concern in this area.


The easiest way to standardize the chain of custody of test samples is to use a form similar to Ana-Lab's Chain of Custody. The content of the forms clearly identifies:

1. The name/address/telephone number of the customer.

2. Unique sample identifiers.

3. Clear instructions for the tests required upon the samples.

4. A section stating concisely the actual chain of custody of the samples. This includes provisions for the name of personnel, dates and times of relinquishment / receipt of the samples, etc.

The chain of custody procedure is intended to ensure that the sample is kept secure at all times and will stand up to the documentation requirements that may be associated with legal challenge. The chain of custody document identifies the location, transfer, and security of the sample from collection to disposal and provides documentation that identifies each person having true possession of the sample. Therefore, this chain of custody exists before and after a sample arrives at the laboratory.

Click here to download an Ana-Lab Chain of Custody form.

Click here to download an example of a properly filled out Chain of Custody form.

Click here to download the Standard Terms & Conditions Agreement

For TCEQ's Lead/Copper Chain of Custody form (Form 20683) and Water Quality Parameter Chain of Custody form (Form 20679), please see TCEQ's Drinking Water Lead and Copper Program at:

TCEQ's Water Quality Parameter Chain of Custody form:

TCEQ's Lead/Copper Chain of Custody Form:



Samples taken are then sealed prior to transport to the laboratory. These seals are designed to clearly identify any tampering with the samples prior to their arrival at the laboratory.