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When a police department collects physical evidence at a scene, that evidence enters a documented chain that must hold up under legal scrutiny months or years later in court. The bag the evidence is collected into — and the documentation accompanying it — is the foundation of that chain.
Chain of custody bag requirements specify what a department’s evidence packaging must include: tamper evident seals, sequential numbering, write-on documentation panels, and material standards. Departments that fail to meet these requirements risk having evidence challenged or suppressed at trial — which can mean the difference between a successful prosecution and a case that falls apart in the courtroom.
This guide covers the core requirements every police department should ensure their chain of custody bags meet.
The primary requirement: the bag must reveal any attempt at unauthorized access. The adhesive seal at the bag’s closure should bond permanently when pressed closed. Attempts to lift, peel, or remove the seal must produce visible damage — torn film, void messaging (“VOID,” “TAMPERING DETECTED”), peeled adhesive that can’t be hidden.
Quality tamper evident seals use multi-layer construction where the void messaging is hidden in a separate layer beneath the adhesive. When the seal is intact, the layers align and the void message is invisible. When the seal is disturbed, the layers separate and the void message becomes permanently visible.
Every chain of custody bag should carry a unique sequential number printed prominently on the bag body. The number ties the bag to specific case files, evidence logs, and chain of custody records. Sequential numbering also creates a check against bag substitution — auditors can verify that the bag presented at trial matches the bag documented at collection.
Most departments use sequential numbering tied to evidence management software. Tear-off receipts with matching numbers let collecting officers retain a record while the bag goes into evidence storage.
The bag must have a structured write-on documentation panel for recording chain of custody information. Typical required fields:
Chain of custody bags must be durable enough to survive years of storage without degrading. Material requirements include:
One of the most important chain of custody requirements involves matching the bag material to the evidence type. As covered in our evidence bag vs property bag guide, paper and plastic evidence bags serve different forensic purposes.
Paper bags are required for biological evidence and items containing biological samples. Paper breathes — it allows airflow that prevents the bacterial and fungal growth that destroys DNA and other biological material in sealed plastic environments. Required for:
Plastic tamper evident bags are appropriate for non-biological items. Plastic packaging is tear-resistant, waterproof, and offers visible tampering detection that paper bags can’t match. Used for:
Departments need multiple bag sizes in their procurement to handle the range of evidence collected. Common sizes:
Chain of custody bag requirements are part of a broader documentation framework. The bag is one piece; the supporting documentation includes:
The bag’s documentation panel supports this broader framework. Many departments use evidence management software that integrates the bag’s sequential number with the department’s case management system, creating a complete digital and physical audit trail.
Departments sometimes use generic Ziploc bags or standard plastic bags for evidence collection in field situations. These bags lack tamper evident seals and proper documentation panels, creating chain of custody gaps that defense attorneys can exploit. Even in field emergencies, departments should maintain stock of proper evidence bags.
Bags sealed without complete chain of custody documentation create gaps in the evidentiary record. Missing case numbers, illegible signatures, undated transfers — any of these can be the basis for a suppression motion at trial. Train officers and intake staff to complete documentation panels fully and legibly.
Biological evidence in plastic bags loses evidentiary value as DNA degrades. Non-biological evidence in paper bags loses tamper evident protection. Match the bag to the evidence — paper for biological, plastic for non-biological.
Evidence transferred to new bags without proper documentation creates chain of custody breaks. If a bag must be re-bagged (damage, deterioration, or operational reasons), document the transfer thoroughly with signatures from both the originating and receiving custodians.
Once sealed, a chain of custody bag should never be reopened without documented authorization and a witness. Reopened bags must be re-sealed in a new bag with full chain of custody documentation of the transfer. Unauthorized re-opening creates an unrecoverable break in the chain.
Departments need a range of bag sizes to handle the range of evidence collected. Stock at minimum: small (5×9), mid (9×12), and large (15×20) bags. Add paper evidence bags for biological evidence and side-by-side bags for combined evidence/property collection.
Multiple bag suppliers across a single department creates inconsistencies in documentation panels, sequential number ranges, and bag quality. Standardize on one supplier with proven quality and reliable supply.
Pack quantities of 100 or 50 simplify reordering and inventory management. Annual usage forecasts help determine optimal pack quantities for each bag type.
Most departments justify custom-printed bags with agency name, sequential number ranges specific to the department, and standardized documentation field layouts matching their case management system.
Field officers should always have evidence bags available in their vehicles. Maintain consistent stock levels across patrol vehicles and central evidence collection points.
The bag must be re-bagged in a new evidence bag with complete chain of custody documentation of the transfer. The broken-seal bag is retained as part of the evidence record. The chain of custody form documents the re-bagging event, including the reason for the seal break and the officers who witnessed it.
Different documentation panels make standalone evidence and property bags more appropriate for each use. As covered in our evidence bag vs property bag guide, departments should stock both. Side-by-side combination bags exist for situations where both are collected simultaneously.
Requirements vary by jurisdiction, but the core elements — tamper evident seals, sequential numbering, complete documentation, chain of custody handoffs — are consistent. Departments should consult with their prosecuting attorney’s office on local requirements.
Quality tamper evident bags maintain their seal integrity for years under proper storage conditions. For long-term evidence retention spanning decades, departments should periodically inspect older bags and document any signs of degradation. Bags showing fading print, brittleness, or compromised seals should be re-bagged.
Generic Ziploc bags cost cents each but provide no chain of custody protection. Proper tamper evident evidence bags cost slightly more per unit but justify the cost through their evidentiary value. The math favors quality bags: a single suppression motion lost because of bag inadequacy costs the department far more than years of proper bag procurement.
Since 1980, Superior Bag has manufactured chain of custody bags for police departments and law enforcement agencies across North America. Our patented D-Tec™ closure delivers reliable tamper evidence on every evidence collection.
Our law enforcement product lines:
Request a law enforcement sample packet to evaluate bag styles before placing a bulk order.
For related guidance, see our evidence bag vs property bag guide and our complete tamper evident bag technology guide.
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