OpenTimestamps anchors document hashes into Bitcoin blocks at negligible cost, creating proof of existence that requires no trusted timestamping authority and no recurring subscription to verify. As of 2025, courts accepted Bitcoin-timestamped evidence as valid proof of prior existence in at least one copyright infringement case (AZ Factory). A March 2026 peer-reviewed framework in Frontiers in Blockchain proposes extending blockchain-anchored chain-of-custody to digital evidence in war crimes prosecutions — where evidence is typically captured by civilians in environments with no functioning institutions to issue traditional timestamps. The structural property is specific: a document hash committed to Bitcoin block N can be independently verified by anyone at any future time using only the block header, with no API, no certificate authority, and no continued operation of any company.