You have no doubt heard about Chain of Custody (COC) issues in the many forensic TV shows on our screens. The shows where faulty documentation destroys an otherwise carefully prepared case and the criminal goes free!  So exactly what is a COC?  It is the chronological ‘paper’ trail, showing the collection, transfer, receipt, analysis, storage, and disposal of a sample. At all stages, the sample is in someone’s custody—that person is responsible for it.

The COC is just as important in environmental  and agricultural sciences -the integrity of the sampling, testing and reporting chain is very important, as the test results might also be used as evidence in court cases. For example, if a factory is accused of dumping toxic waste that runs into rivers and makes people ill, any samples taken to prove or disprove this must be handled correctly from ‘A to Z’ , as indicated by the COC.

Field sampling is an important part of the environmental and agricultural sciences and evidence of this is the first step shown in a COC.   Samplers might collect anything from invertebrates and algae samples from rivers for ecological sampling, crop seed samples for analysis, mine bore water samples or contaminated soil samples from reclamation projects. Sampling procedures usually follow government, EPA or other standard guidelines and the samples are logged on the required forms. Samples are often collected in special containers including sterile jars, bottles with preservatives (to try and minimise the degradation of the sample), vials for organic testing etc. Once sampled, they must be correctly stored (often at temperatures <6^oC) and they can then be transferred to a laboratory (lab) for testing (second step in the COC). At the lab, the sample receiver will check the integrity and storage of the sample and will log the sample in for testing (step 3).

 An example of a COC for sample collection, delivery and receipt at a testing lab is shown above. All respective sections have to be completed and signed off by the relevant person (sampler, transporter and lab receiver—all shown encircled in red). Once in the lab, the storage, testing, reporting and disposal must all be similarly controlled, with each step in the process correctly documented.

To find out more about environmental sampling and testing, have a look at our Environmental-Chemistry course which starts at basics and leads you into  the fascinating world of chemicals in our environment. Or check out our Environmental-assessment course.