The Source for Crime and Justice Data

Restricted Data

What is restricted data?

Although available without cost, NACJD data collections are not public-use data, because before using NACJD data, users agree to abide by Federal laws and scientific standards regarding human subject use. Foremost among these, users agree to analyze NACJD data solely for statistical research purposes, not to identify individuals. Therefore, all NACJD data collections have restrictions on their use. Additional restrictions are placed on some collections, where access to the collection is restricted.

Restricted access data are studies or parts of studies that NACJD does not allow users to download for confidentiality reasons. This is indicated on the download page. If only documentation or codebooks are listed, the study is restricted access data. (If downloadable data are listed, the study is restricted use data, which must be used responsibly.)

Why is access to some data restricted?

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. This is done in accord with ICPSR policy, University of Michigan policy, and U. S. Department of Justice regulations (28 CFR 22) (PDF 45K) and Federal law (42 USC 3789(g)). Blanking or otherwise modifying the values of direct or indirect identifying variables are measures sometimes taken to assure the protection of confidentiality. Occasionally, a study will require extra measures.

In such instances, the unmodified data is placed in what is referred to as the Restricted Access Data Archive. These collections or parts of collections are not publicly available through the NACJD or ICPSR websites.

Access to these collections is possible but only upon additional written certifications. Using a Restricted Data Use Agreement, available online as a PDF file, prospective data users must certify in writing that the data will be used for research or statistical purposes only, and that the confidentiality of respondents or subjects will be protected.

In addition, they must describe why they need the restricted access data, and how they plan to protect it from physical and virtual theft. The request must be signed by a researcher with a permanent faculty appointment, and by a representative of the researcher's university or other institution, e.g., Dean or President. The forms must also be accompanied by a letter from the institution's Institutional Review Board office, indicating that a responsible officer has reviewed the request and finds the project's terms of use for the requested data to be in compliance with the receiving organization's human subject and confidentiality rules. (This is not necessarily the same as a full IRB review. An official determination that the project's request is exempt from IRB review is also acceptable, if that is in keeping with the organization's standard practice.) Please note that the final determination on access to restricted data rests with NACJD, and that NACJD does not ship data to addresses outside of the United States, nor permit the transfer of data to anyone outside of the United States.

Special Situations

University students may gain access to the restricted data, but a faculty advisor must serve as Restricted Data Investigator. The faculty advisor and institution bear full responsibility for ensuring that all conditions of the agreement are met by the student, who must sign the Supplemental Agreement With Research Staff form. (See Forms to Request Restricted Data.)

Unaffiliated scholars, freelance consultants, employees of research organizations not affiliated with a university must make arrangements to fulfill the IRB requirement. In some cases, a coinvestigator with a university affiliation must request the data; in others, the confidentiality safeguards of the organization employing the researcher may be considered sufficient. Applicants in these situations should be particularly careful to provide full details of their plans for use of the data and for safeguarding it.

Coinvestigators from different organizations must each make a separate request for the data, complete with a data protection plan and the required signatures. Each request should refer to the fact that the researchers will be working together. The only situation in which the Supplemental Form for Research Staff is sufficient to allow multiple researchers access to the data is where there is one primary researcher who is in a position to supervise the use of the data by all others, and has the authority to discipline them for misuse.

List of Restricted Access Data Collections

There are two types of data collections in the restricted access archive:

  1. Partially restricted. These studies are currently available to the public, but certain sensitive variables have been restricted. Users should first refer to the downloadable, public use version of the collection to determine if it will serve their research purposes and to find out which variables have been restricted. If the restricted variables are necessary, users can request the restricted version.

  2. Completely restricted. In many cases, the documentation files for the studies are publicly available so users can determine if a particular study will be useful for their research.

Requesting Restricted Access Data

To request data, use the link in the Access Notes on the study home page for a particular study to connect to the ICPSR Restricted Use Data Contract Portal.