Evidence Collection, Preservation, and Chain of Custody
Evidence Collection, Preservation, and Chain of Custody
This domain tests how evidence is recognized, collected, packaged, marked, stored, and transferred so that it remains admissible. Expect questions on packaging choices, chain-of-custody forms, laboratory submission, and the effect of a documented break in custody.
Types and relevance
Evidence may be testimonial, documentary, real, or demonstrative. Direct evidence proves a fact without inference; circumstantial evidence requires inference but is equally admissible. Exculpatory evidence must be preserved and disclosed. The agent must show relevance, authenticity, and a proper foundation before evidence is admitted.
Collection and packaging
Photograph and document before collection. Use gloves and change them between items. Biological evidence must be air-dried and packaged in paper, never sealed wet in plastic. Firearms are rendered safe, unloaded, and packaged separately from ammunition. Drugs are weighed, sealed, and labeled. Digital devices are placed in anti-static packaging and kept away from heat and magnetic fields. Each item receives a unique number, date, initials, and a description.
Chain of custody
The chain documents every transfer: from whom, to whom, date, time, purpose, and signatures. DA Form 4137 is the Evidence/Property Custody Document; DA Form 4002 is the evidence tag. A seal is initialed and dated. If a seal is opened, the opener documents it and reseals with a new seal. The evidence custodian maintains secure storage and a log.
Laboratory submission
The U.S. Army Criminal Investigation Laboratory examines DNA, latent prints, firearms, trace, and controlled substances. Submissions should include known reference samples, control samples, and a clear request. The agent keeps a copy of the submission and tracks the return.
Worked example
A bloodstained shirt is found at a scene. The agent photographs it in place, air-dries it, places it in a paper bag, seals and initials the bag, completes a DA Form 4002 tag and a DA Form 4137 entry, and transports it to the evidence room. When the laboratory opens the bag, the examiner documents the seal and re-seals the contents. The agent's testimony can then account for every transfer.
Traps that cost marks
Plastic for biological evidence. Sealing an item before it dries. Missing reference samples. Unsigned or undated transfers. Treating a small gap as harmless without explanation. Failing to document negative findings.