7 Digital evidence retention is the policy that quietly determines most of an agency’s storage bill. How long each video, image and extraction is kept decides how much capacity accumulates, how much it costs and how much legal exposure the agency carries. Keep too little and a case can collapse; keep everything forever and storage costs climb every year while records requests and discovery get harder to answer. There is no single national rule. Retention is set by a patchwork of state statutes, records schedules, case law, court rules and agency policy. This article explains the forces that shape digital evidence retention, how agencies typically structure schedules and what those choices mean for the storage underneath. What drives digital evidence retention Several obligations overlap, and the longest one usually wins: State records retention schedules issued by state archives or records commissions set minimum periods for categories of public records, including recordings. Body camera statutes in many states set specific minimums. California Penal Code 832.18, for example, recommends at least 60 days for non-evidentiary body camera data and at least two years for recordings involving use of force, arrests or complaints, with access and deletion logs kept permanently. Criminal case lifecycle. Evidence generally must be kept through investigation, charging, trial, sentencing, appeal and any post-conviction proceedings. Statutes of limitations. For offenses with no limitation period, such as murder in most US jurisdictions, related evidence may need to be preserved indefinitely, especially for unsolved cases. Preservation statutes. Many states have laws requiring preservation of biological evidence in serious cases, and agencies often apply similar caution to associated digital files. Civil litigation and legal holds. Footage tied to a claim or lawsuit must be preserved until the matter is resolved, regardless of the normal schedule. Agency policy and transparency commitments, which often exceed statutory minimums. Because rules differ by state and change over time, retention schedules should be reviewed with the prosecutor’s office, county or city counsel and the state records authority. How agencies structure retention schedules Most agencies group digital evidence into categories, each with its own period. A typical structure looks something like this (periods vary by jurisdiction): Non-evidentiary recordings with no enforcement action or complaint: weeks to a few months. Citations and minor incidents: often a year or two, or until the case closes plus a margin. Misdemeanor cases: through disposition plus the appeal window. Felony cases: through sentence completion and appeals, often many years. Homicide, sexual assault and unsolved serious crimes: frequently indefinite. Use of force, officer-involved shootings and complaints: often longer than the related case, to cover civil claims and internal review. The key is accurate categorization at upload. Footage left uncategorized often defaults to the longest period, which inflates storage and makes defensible deletion harder. The general principles are covered in data retention policy best practices. Why digital evidence retention is a storage design problem Retention periods translate directly into capacity. If an agency adds 300 TB of new footage a year and keeps evidentiary material for an average of three years, steady-state storage for that category alone approaches 900 TB, before replicas. Indefinite categories never age out, so they grow every year. Our guide to body-worn camera storage works through a full example. Retention also changes which storage features matter: Retention locks. Write-once controls prevent deletion or modification before the retention date, protecting against mistakes, insiders and ransomware. Legal holds that override normal expiry for specific files or cases without changing the schedule for everything else. Lifecycle policies that move older evidence to lower-cost tiers automatically. The mechanics are explained in S3 lifecycle policy and data lifecycle management. Media longevity. Evidence kept for decades will outlive several generations of hardware. Storage that can be refreshed node by node, without migrating the archive in one large project, reduces risk. Retention planning should also account for copies. Every replica, backup and redacted version inherits the obligation of the original, and when the original is deleted on schedule, those copies need to expire with it. Otherwise the agency keeps paying for data it has formally disposed of, and a records request can surface footage the agency believed was gone. Defensible deletion Deleting evidence on schedule is as important as keeping it. Holding footage longer than required increases storage cost, broadens public records exposure and can complicate discovery. But deletion has to be defensible: the agency should be able to show what was deleted, when, under which rule and that no hold applied. That requires: A documented schedule approved by counsel and the records authority. Automated expiry tied to case status, not manual cleanup. Hold checks before deletion. Permanent logs of deletions, which some statutes explicitly require. Verifying that deleted data is actually gone is its own discipline, described in data deletion verification. Retention for evidence beyond video Body camera footage gets most of the attention, but retention schedules have to cover every digital evidence type the agency holds: Interview room recordings are often tied to the case and may need to be kept as long as any other evidence in a serious felony. Mobile device extractions and computer forensic images can be very large and may contain data about people unrelated to the case, which argues for careful scoping and timely disposal once the case allows it. Third-party video from businesses and residents should be categorized at intake like any other evidence, with its source documented. 911 audio, radio traffic and dispatch records usually fall under separate records schedules but are frequently linked to cases. Drone imagery may be subject to specific local policies on retention and public access. Linking every item to a case number, rather than storing it as a standalone file, lets one change in case status drive the retention of all related evidence together. Common digital evidence retention mistakes The same problems appear again and again in audits and records reviews: Defaulting uncategorized files to “keep forever”, which hides storage growth and makes deletion legally risky later. Manual deletion projects run once a year, which are slow, inconsistent and hard to document. Retention settings that differ between the evidence application and the storage layer, so files expire in one place but not the other. Forgetting copies: redacted versions, discovery exports and backups that outlive the original. No review after law changes, leaving schedules out of date for years. Retention across hosting models Retention looks different depending on where evidence lives. In a vendor-hosted cloud, retention rules are usually configured in the evidence application, and the agency depends on the vendor to honor them and to export data at contract end. On-premises or hybrid storage gives the agency direct control over retention locks and deletion, at the cost of running the platform. Our comparison of cloud DEMS vs on-prem evidence storage covers the trade-offs, and backup retention changes explains why changing retention after the fact is harder than it looks. Checklist: building a digital evidence retention program Inventory every evidence source and category. Map each category to the longest applicable statutory, records and policy requirement. Get the schedule reviewed by the prosecutor’s office and counsel. Require categorization at upload and audit uncategorized files regularly. Use write-once retention locks for evidentiary categories. Implement legal holds that suspend expiry without changing the schedule. Automate deletion with permanent logs. Model storage growth for indefinite categories over at least five to ten years. Review the schedule whenever state law or agency policy changes. Putting it together Digital evidence retention is where legal obligations, public trust and storage economics meet. A clear schedule, accurate categorization, enforceable retention locks and defensible deletion keep the agency compliant without paying to store everything forever. Because many categories last years or never expire, the storage platform has to be designed for decades of growth and hardware refreshes, not just the next budget cycle. Frequently asked questions Is there a federal rule for how long digital evidence must be kept? No single federal rule covers all agencies. Retention is mostly set by state law, state records schedules, case requirements and agency policy. Can agencies delete body camera footage after a set period? Yes, if the footage is non-evidentiary, no hold applies and the minimum period under state law and policy has passed. Deletion should be logged. Why is homicide evidence often kept indefinitely? Murder typically has no statute of limitations, and evidence may be needed for future prosecutions, appeals or post-conviction review, so agencies preserve it without an end date. What is a legal hold? A legal hold suspends normal deletion for specific evidence because of litigation, an investigation or a records request. It must override the schedule until it is released. How does retention affect storage cost? Longer retention means more data on hand at any time. Indefinite categories never age out, so they add capacity every year. Further reading Digital evidence storage Body-worn camera storage Chain of custody for digital evidence Cloud DEMS vs on-prem evidence storage Data retention policy best practices
