By Peter Leasure, J.D., Ph.D.*
Several have proposed blockchain-based criminal record databases or discussed their potential benefits, including the National Center for State Courts. These authors generally point to several benefits of utilizing blockchain-based criminal record databases including decentralization and immutability. Generally speaking, decentralization means that data is stored on multiple interconnected nodes and that a failure or breach of a single node (or even perhaps multiple nodes) will not compromise the data. Immutability (often referred to as the append-only feature) means that once data is on a specific block of a blockchain, it cannot be reversed, changed, or deleted. The focus of this piece is on immutability.
While true immutability may seem like an attractive feature of a blockchain-based criminal record database, many jurisdictions within the U.S. have laws that allow for the sealing or expungement of one’s criminal history. Sealing generally means that the record is ordered to be hidden from public view and expungement generally means that the record is ordered to be destroyed. With true immutability, records on a blockchain could not be removed from public view or destroyed. A new block could certainly be added to the blockchain noting that the previous record is no longer valid; however, this approach defeats the overall purpose of record sealing and expungement. Therefore, because of sealing and expungement laws, a truly immutable blockchain-based criminal record database may not be the best approach.
Relatedly, while some have stated that issues of manual data entry and quality control could be alleviated using blockchain technology (largely because there would be a single immutable database for all criminal justice partners to amend), it is difficult to imagine how blockchain technology could meaningfully reduce data entry errors or reduce the need for quality control in practice. Each occurrence of arrest, court processing, and potential post-sentence processing would still need to be manually entered by criminal justice personnel (it is difficult to imagine an error-proof artificial intelligence mechanism), and manual entry is always subject to error and in need of quality control and additional alterations. Here again, the need for a mutable blockchain-based criminal record database is reinforced.
Interestingly, some have recognized the issues of immutability noted above and have presented or discussed methods to erase or delete information contained in blockchains. Nonetheless, any alterations to previous blocks would still need consensus from participants in the network, and consensus could be more difficult on a public blockchain. Given these points, a hybrid, private, or consortium blockchain may be best suited for a blockchain-based criminal record database. In summary, while blockchain technology does present some interesting features, jurisdictions should thoroughly examine the potential costs, benefits, and practical impacts of implementing a blockchain-based criminal record database and weigh those factors against the features of other types of databases.
* Peter Leasure is a Senior Research Associate at the Drug Enforcement and Policy Center, Moritz College of Law, The Ohio State University.
 Maisha Afrida Tasnim et al., CRAB: Blockchain Based Criminal Record Management System, in Security, Privacy, and Anonymity in Computation, Communication, and Storage 294, 294-303 (Guojun Wang, Jinjun Chen, & Laurence T. Yang eds., 2018); Aditya Vijaykumar Singh et al., A Criminal Record Keeper System using Blockchain, in 2022 6th International Conference on Trends in Electronics and Informatics (ICOEI) 840 (2022); Aastha Jain et al., Blockchain-Based Criminal Record Database Management, 2021 Asian Conference on Innovation in Technology, 1-5 (ASIANCON) (2021); Alejandro Tomás Dini et al., Analysis of implementing blockchain technology to the argentinian criminal records information system, in 2018 Congreso Argentino de Ciencias de la Informática y Desarrollos de Investigación, 1-3 (CACIDI) (2018); Merritt Francis, Blockchain as Best Practice: The Benefits of the Criminal Justice System Implementing Blockchain Technology, Richmond Journal of Law and Technology (2022), https://jolt.richmond.edu/2022/01/06/blockchain-as-best-practice-the-benefits-of-the-criminal-justice-system-implementing-blockchain-technology (last visited Oct 13, 2022); Paul Embley, When Might Blockchain Appear in Your Court?, Trends in State Court, 28-34, (2018).
 It is important to point out that some mistakenly identify Satoshi Nakamoto (the name used by the person or group of people that published the Bitcoin whitepaper) and Bitcoin as the origin of blockchain technology (see Francis, 2022 noted above). However, papers discussing what would later be termed blockchain technology were published much earlier; See Stuart Haber & W. Scott Stornetta, How to Time-Stamp a Digital Document, in Advances in Cryptology, 437-455 (Alfred J. Menezes & Scott A. Vanstone eds., 1991); Dave Bayer, Stuart Haber & W. Scott Stornetta, Improving the Efficiency and Reliability of Digital Time-Stamping, in Sequences II 329 (Renato Capocelli, Alfredo De Santis, & Ugo Vaccaro eds., 1993), http://link.springer.com/10.1007/978-1-4613-9323-8_24 (last visited Oct 13, 2022).
 Praveen Jayachandran, The difference between public and private blockchain, IBM Supply Chain and Blockchain Blog (2017), https://www.ibm.com/blogs/blockchain/2017/05/the-difference-between-public-and-private-blockchain/ (last visited Oct 13, 2022) (It is important to note that immutability is a feature of both public and private blockchain a public blockchain. With a public blockchain, anyone is allowed to participate in the network. With a private blockchain, only invited entities are allowed to participate in the network. Participation can mean many things, but generally means validating the authenticity of blocks to be added to the blockchain. There can also be hybrid blockchains (a mix of public and private) and consortium blockchains (private but multiple organizations participate)); See Omar Dib et al., Consortium Blockchains: Overview, Applications and Challenges, International Journal On Advances in Telecommunications, 51-64, (2018); Henry M. Kim et al., Permissionless and Permissioned, Technology-Focused and Business Needs-Driven: Understanding the Hybrid Opportunity in Blockchain Through a Case Study of Insolar, 69 IEEE Transactions on Engineering Management 776 (2022).
 Eviction Record Expungement Can Remove Barriers to Stable Housing, Center for American Progress, https://www.americanprogress.org/article/eviction-record-expungement-can-remove-barriers-stable-housing (last visited Oct 13, 2022) (Noting that some jurisdictions allow or may allow for sealing or expungements of civil actions such as evictions).
 Merritt Francis, Blockchain as Best Practice: The Benefits of the Criminal Justice System Implementing Blockchain Technology, Richmond Journal of Law and Technology (2022), https://jolt.richmond.edu/2022/01/06/blockchain-as-best-practice-the-benefits-of-the-criminal-justice-system-implementing-blockchain-technology (last visited Oct 13, 2022).
 Martin Florian et al., Erasing Data from Blockchain Nodes, in 2019 IEEE European Symposium on Security and Privacy Workshops (EuroS&PW) 367 (2019); Peter Hillmann et al., Selective Deletion in a Blockchain, arXiv e-prints (2021), https://ui.adsabs.harvard.edu/abs/2021arXiv210105495H (last visited Oct 13, 2022); Eugenia Politou et al., Blockchain Mutability: Challenges and Proposed Solutions, 9 IEEE Transactions on Emerging Topics in Computing 1972 (2021); Arthur Carvalho et al., When good blocks go bad: Managing unwanted blockchain data, 57 International Journal of Information Management 102263 (2021); See Jing Chen & Silvio Micali, Algorand: A secure and efficient distributed ledger, 777 Theoretical Computer Science 155 (2019) (noting that blockchains with a lower probability of forking may have advantages over those with higher probabilities of forking).
 Bahareh Lashkari & Petr Musilek, A Comprehensive Review of Blockchain Consensus Mechanisms, 9 IEEE Access 43620 (2021) (discussing various consensus mechanisms).
 Martin Florian et al., Erasing Data from Blockchain Nodes367 (2019), https://www.computer.org/csdl/proceedings-article/euros&pw/2019/302600a367/1cJ7azLFB0A (last visited Oct 13, 2022).
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