7 Cloud DEMS vs on-prem evidence storage is one of the biggest infrastructure decisions a large law enforcement agency makes. A digital evidence management system (DEMS) is the application officers, investigators and prosecutors use to upload, tag, review, redact and share evidence. The storage underneath it holds every file for years. Agencies can buy both as a hosted service, run both themselves, or combine a hosted or on-premises application with storage the agency controls. There is no universal answer. Small agencies often benefit most from a fully hosted model. Large city, county and state agencies, with hundreds of terabytes or more of retained evidence, face a different calculation. This article lays out the trade-offs. What each model looks like Fully hosted cloud DEMS The vendor runs the application and stores the evidence in its cloud, usually priced per officer or per device with storage tiers or “unlimited” plans. The agency manages users and policies, not infrastructure. On-premises DEMS and storage The agency (or its city or county IT department) runs the evidence application and the storage in its own or a government data center. It controls hardware, retention locks, encryption keys and network access. Hybrid The application may be hosted or on-premises, while some or all evidence sits on storage the agency controls, often an S3-compatible object store. Another hybrid pattern keeps recent evidence in the cloud and moves older material on premises, or keeps a second copy in a different location. Cost over the life of the evidence Hosted pricing is predictable in the first contract term and avoids capital spending. The question is what happens over ten years as retained evidence accumulates. Per-officer plans with storage caps can trigger overage charges; “unlimited” plans tend to be priced to cover expected growth. Agencies should model total cost against their own projected retained volume, not today’s. On-premises storage requires upfront investment, staff time and periodic hardware refresh, but the cost per retained terabyte often falls as capacity grows, especially with dense object storage on standard servers. A useful exercise is to compare cost per terabyte retained per year under each model at year one, year five and year ten. The framework in total cost of ownership for data storage applies, and storage cost per terabyte explains how to calculate it consistently. Hidden costs show up on both sides. Hosted models can involve export or egress fees for large discovery requests or contract exit (see egress vs ingress). On-premises models carry power, space, staffing and replacement cycles. Security and CJIS compliance Both models can meet the FBI CJIS Security Policy. Reputable hosted providers sign CJIS addenda, screen personnel and encrypt data. On-premises deployments put the agency directly in control of encryption, access and audit, which some agencies prefer for sensitive investigations. As of 2026 the policy is in its 6.x series, with version 6.1 (June 2026) raising minimum encryption strength for several controls to 256-bit; either model must keep up with those changes. Questions to ask any provider include where data physically resides, who holds the encryption keys, how quickly the agency can obtain logs during an investigation of misuse, and how breaches are reported. Control, sovereignty and exit risk Evidence outlives contracts. Footage collected today may be needed long after the current vendor agreement ends. That makes exit planning central to cloud DEMS vs on-prem evidence storage decisions: How is evidence exported, in what formats, with which metadata and hashes? How long does a full export take at the agency’s volume? What does it cost? Is chain of custody preserved through the export? On-premises and hybrid models reduce this exposure because the evidence already sits on infrastructure the agency controls. Cloud exit planning and how to avoid cloud lock-in cover the general principles, and cloud repatriation strategy explains what moving data back looks like in practice. Regional and state partnerships add another wrinkle. Some agencies share evidence platforms with neighboring jurisdictions or prosecutors’ offices, which spreads cost but complicates questions about who controls the data and who decides when it moves. Performance and access Investigators need fast access to recent evidence; prosecutors need bulk export for discovery. Hosted platforms depend on internet bandwidth, which can be a bottleneck for very large uploads from stations or for multi-terabyte case files. On-premises storage on the agency network avoids that but requires the agency to build for remote access by partner agencies and prosecutors. Many agencies end up with a mix: local ingest and storage, with controlled sharing outward. Resilience and ransomware Hosted providers replicate data across their facilities. On-premises deployments need their own plan: replication to a second site, immutable retention locks and ideally an isolated copy. Local government has been a frequent ransomware target, so evidence storage should not share credentials or flat networks with general IT systems. Moving between models Agencies rarely make this decision once. A department may start with a fully hosted body camera bundle, then reconsider when retained evidence reaches hundreds of terabytes or a contract comes up for renewal. Moving evidence between models is a project in its own right: Inventory first. Know how much evidence exists by category, how much is under legal hold and how much can be deleted before moving anything. Move in phases. Closed and archived cases can often move first, while active cases stay put until they settle. Verify every object. Hash before export and after import, and keep the verification records as part of the chain of custody. Keep metadata intact. Case links, categories, retention dates and audit history matter as much as the video itself. Plan bandwidth and time. At petabyte scale, network transfer can take months; physical transfer devices are sometimes used. Agencies that expect to change models later can reduce the pain now by insisting on open formats, documented export tools and storage that speaks a standard interface such as the S3 API. Questions to ask before signing Whichever model is chosen, a few questions separate a sound contract from a future problem. What is the full price at the agency’s projected volume in year five and year ten? Who owns the encryption keys? Where is each copy of the evidence physically stored? What happens to the data if the contract ends or the vendor is acquired? How are retention locks and legal holds enforced, and can the agency prove it? Getting written answers before signature is far easier than negotiating them afterwards. When each model tends to fit Fully hosted often fits small and mid-sized agencies without dedicated infrastructure staff, or agencies early in a body camera program. On-premises or hybrid often fits large agencies with hundreds of terabytes to petabytes of retained evidence, existing government data centers, strong IT teams, or policies requiring local control of keys and data location. It also fits agencies that want the freedom to change evidence applications without moving the archive. Our article on body-worn camera storage shows how quickly volumes reach that scale. Checklist: comparing cloud DEMS vs on-prem evidence storage Model ten-year cost per terabyte retained under each option. Confirm CJIS addenda, encryption strength and key ownership. Document data location and sovereignty requirements. Test export: format, metadata, hashes, speed and cost. Check that retention locks and legal holds are enforceable and auditable. Assess bandwidth for ingest and discovery exports. Plan replication, immutability and ransomware isolation. Confirm the DEMS can use agency-controlled storage (for example over the S3 API) if a hybrid model is likely. Include staffing, power, space and refresh cycles for on-premises options. Putting it together Cloud DEMS vs on-prem evidence storage is less about which technology is better and more about who carries the long-term cost and control of evidence that must last for years. Hosted models simplify operations; on-premises and hybrid models give large agencies more control over cost growth, keys, data location and exit. Many large agencies settle on a hybrid: a capable evidence application on top of storage they own. For the full set of requirements, see our hub on digital evidence storage. Frequently asked questions Is cloud DEMS CJIS compliant? It can be, when the provider signs a CJIS addendum and meets the policy’s technical and personnel requirements. The agency remains responsible for verifying compliance. Is on-prem evidence storage cheaper? At small scale, usually not once staffing and hardware are counted. At large scale with long retention, cost per retained terabyte can be lower on premises. Model your own volumes. Can a hosted DEMS use agency-owned storage? Some evidence platforms support external or S3-compatible storage targets. Ask vendors directly, as support varies. What is the biggest risk with fully hosted evidence storage? Exit risk: moving years of evidence with metadata and chain of custody intact can be slow and costly if not planned upfront. How do agencies combine both models? Common patterns include keeping recent evidence in a hosted DEMS and archiving older material on premises, or running the DEMS on agency infrastructure with a replica elsewhere. Further reading Digital evidence storage Body-worn camera storage Digital evidence retention Chain of custody for digital evidence CJIS compliant storage
