Prior to public release, the National Archive of Criminal Justice Data routinely checks all its data collections for conditions that might lead to violation of confidentiality of respondent and subject data. The issue of confidentiality applies to a variety of data including personal interviews, observation records, notes, recordings, organizational and institutional data, location or geographic coordinate data, and public records. Respondent confidentiality is ensured by removing, masking, blanking, or collapsing direct or indirect identifying variables within public-use versions of the datasets.
However, not all datasets are available for public access because there remains a risk that the identity of research participants could be disclosed. In such instances, the data are placed into the Restricted Access Data Archive or the Physical Data Enclave and are not downloadable from the NACJD or ICPSR websites.
In most instances, documentation associated with datasets remains available for public use. Documentation includes the study metadata, in addition to any codebooks, questionnaires, user guides, or other supporting documentation prepared for use with the study.
Types of Access to Restricted Data
- Restricted-use access. These datasets are provided to approved researchers at their institutions, usually for a 24-month period. To access restricted-use versions of datasets, prospective data users must submit an application through ICPSR's online Data Access Request System (IDARS). For more information about how ICPSR determines whether data should be publicly available or restricted, view the Guide to Social Science Data Preparation and Archiving.
- Online analysis access. The Restricted Survey Documentation and Analysis (RSDA) system allows remote access to the data using NACJD's online analysis system. This system allows analysis of the data without access to the microdata and limits the kinds of analysis that can be performed and output provided. Read more about online analysis.
- Virtual Data Enclave (VDE) access. The VDE is a virtual machine launched from the researcher's own computer that operates on a remote server. The virtual machine is isolated from the researcher's computer, which restricts files or parts of files from being downloaded. The virtual machine also restricts external access and prevents users from emailing, copying, or moving files outside the secure environment. These data portals allow users to obtain remote access to restricted data that would not otherwise be available for research. View information about the Virtual Data Enclave.
- Physical Data Enclave access. The Data Enclave is a secure data analysis laboratory that allows access to the original data in a controlled setting on site at ICPSR/University of Michigan. Users interested in utilizing data available as enclave-only must complete an Application for Use of the ICPSR Data Enclave (PDF 149KB). Applications require approval from the Investigator's Institutional Review Board, and exemptions are not permitted. Once the application has been approved, researchers will need to make arrangements to visit the on-site enclave in the Perry Building at the University of Michigan in Ann Arbor, Michigan. View information about the Physical Data Enclave.