What is chain-of-custody?
Chain-of-Custody (COC) is a documentation trail that demonstrates possession, control, and integrity of a sample at all times. COC is established when:
- The sample is in a person’s physical possession
- The sample is in view of the person after being in possession
- The sample was in physical possession and then locked up to prevent tampering
- The sample is kept in a restricted, secured area
Each transfer of custody must be documented to provide evidence that the sample has not been tampered with or altered in any way. Documentation also ensures that proper sample handling has been maintained and is used to track samples through collection, processing, analysis, and eventual disposal. Each sample will be labeled and assigned a unique identification number. Documentation of temperature control, storage conditions, and tamper proof seals are critical to maintain the integrity of a sample. Documentation for a legal sampling event will include photographs, videos, field notes, and COC forms. Unequivocal documentation is necessary to meet quality control and data defensibility in legal proceedings.
General requirements of COC forms include the sample collector’s name and signature, mailing address and phone number, the name of project manager or person who will receive data, the analytical laboratory’s name and city, and description of each sample (unique identifier, matrix [i.e., soil, water, gas], date and time of collection, and type of analysis required) (Figure 1). The COC must be dated with signatures of individuals involved in the chain of possession. Although environmental laboratories routinely use COC to track samples, it may not satisfy the additional details required for litigious investigations. To meet the requirements of legal COC it is recommended to refer to the ASTM Standard Guide for Sample Chain-of-Custody Procedures (ASTM D4840-99) (ASTM, 2018) .
Why is it important?
The purpose of following Chain-of-Custody procedures is to provide evidence that all samples during collection, transportation, and storage were handled only by authorized personnel and were not available for tampering prior to analysis. COC documentation may serve three purposes 1) analytical instructions between sample collection personnel and the analytical laboratory, 2) record of samples provided to the laboratory, 3) documentation for litigation cases. For legal investigations, all personnel involved with the custody of samples should have prior training on COC procedures. Any break in the chain-of-custody can invalidate the samples as evidence.
- Polychlorinated Biphenyls (PCBs)
- Incidental PCBs
- Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs, Dioxins)
- Polycyclic Aromatic Hydrocarbons (PAHs)
- Ignitable Liquid Residue (ILR)
- Petroleum Hydrocarbons (TPH/PHC F1 to F4)
- Benzene, Toluene, Ethylbenzenes, Xylenes (BTEX)
- Natural Toluene
- Extended Metals
- Volatile Organic Compounds (VOCs)
- Petroleum Gases
- PERC and Chlorinated Solvents
- Persistent Pesticides/ Persistent Organic Pollutants (POPs)
- Creosote and Coal Tar
- Meth and Related compounds
- Per- and Polyfluoroalkyl Substances (PFAS)
- Cannabis/ Marijuana
- Naphthenic Acids
- Legal Sampling
- Study Design
- Data Analysis and Visualization
- Data Wrangling
- Multivariate Statistical Analysis
- Principal Component (PCA); Hierarchical Cluster (HCA)
- Science Communication
- Data Science/Big Data
- Multidimensional Gas Chromatography (GC×GC)
- Source Apportionment
- Chemical Fingerprinting
- Diagnostic Ratios
- Clandestine Laboratories
- Fate and Transport
- Soil gas sampling
- Surface casing vent sampling
- Forensic Genetic Microbiology
- Arsonous Wildfires
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From sample collection to data analysis, the Chemistry Matters team ensures that the entire process is performed with the requirements necessary to overcome legal scrutiny. Executing and documenting an unbreakable chain-of-custody is vital for the legal defensibility of evidence in environmental forensics and arson investigations.