April 2006Volume 7Number 3PDF icon PDF version (for best printing)

Case Synopsis: Southern Illinoisan v. Illinois Department of Public Health

It is not very often that an opinion thoroughly discussing the application of the Freedom of Information Act is published. On February 2, 2006, however, the Illinois Supreme Court issued such an opinion in Southern Illinoisan v. Illinois Department of Public Health.1 


As I am sure you are aware, the Freedom of Information Act (the Act or FOIA) provides a mechanism for someone to obtain copies of documents or records used and maintained in the course of business by a governmental entity or agency in the State of Illinois.2 Of course, this disclosure requirement is subject to specific exemptions.3 The Southern Illinoisan case discusses the exemption for disclosing information specifically prohibited from disclosure by state law and the Illinois Health and Hazardous Substances Registry Act’s (Registry Act) prohibition from disclosing certain information. Although the case discusses a specific statute, there are many points of discussion by the Supreme Court important to any attorney advising his or her client on FOIA compliance. 

The Case

The Southern Illinoisan is a daily newspaper published in Carbondale, Illinois (Plaintiff). The Plaintiff submitted a request for records, pursuant to the FOIA, to the Illinois Department of Public Health (Department) requesting data maintained in the Illinois Health and Hazardous Substances Registry (Cancer Registry).4 The specific data requested was: “type of cancer, zip code and date of diagnosis” to be delivered in this format.5 The Department denied the request and the denial was upheld by the Department Director.6 Subsequently, the Plaintiff filed a complaint in the circuit court seeking review of the Department’s denial.7 While there was a long procedural road before the case reached the Illinois Supreme Court; the Supreme Court identified one question which was the subject of the appeal before them:

whether the information requested from the Department by plaintiff pursuant to FOIA “tends to lead to the identity” of patients listed in the Cancer Registry, thereby violating section 4(d) of the Registry Act.8 

The Department’s main argument for claiming that the information was exempt under FOIA was that the Registry Act prohibits the disclosure of information which reveals the identity, or any group of facts which tends to lead to the identity, of any person whose condition is submitted to the Cancer Registry.9 

In support of their denial, the Department argued that because the Registry Act prohibits disclosure, the information is exempt under section 7(1)(a) of FOIA.10 The Department relied on the expert testimony of Dr. Latanya Sweeney to establish that the identity of persons could be determined from the data set requested. Dr. Sweeney is a professor of computer science and public policy at Carnegie Mellon University and is the director of the University’s Laboratory for International Data Privacy.11 Dr. Sweeney testified that she conducted an experiment to determine if persons listed on the Cancer Registry could be identified from only the three information fields requested by Plaintiff. She compared this data with information readily available to the general public. Using a personal computer and traditional software database, Dr. Sweeney was able to re-identify with a single correct name 18 of 20 sets of data provided—this corresponded to correctly identifying Cancer Registry names 80-87 percent of the time.12 

The Department argued that it was this uncontested evidence that the Cancer Registry information requested by the Plaintiff tends to lead to the identity of cancer patients.13 And, as a result, disclosure of type of cancer, date of diagnosis and ZIP Code violates section 4(d) of the Registry Act and is therefore exempt under section 7(1)(a) of FOIA.

The Court’s Analysis

The Supreme Court noted that Dr. Sweeney’s testimony also indicated that in order to accurately arrive at the 18 of 20 names listed in the Cancer Registry she used a multi-step process. She studied neuroblastoma,14 she purchased and used several publicly available data sets, costing about $2,000. To obtain these data sets she had to complete proper forms, wait for the requests to be processed, and receive the data in the mail in CD-format. She also testified that she had to scrutinize the data sets to identify common factors for neuroblastoma cases, and at one point when she had discovered she made a mistake went back and focused on another factor. She then gathered information from other on-line sources, as well as from libraries and newspaper articles. Dr. Sweeney concluded that it was her opinion that “it is very easy to identify persons from the Cancer Registry using public data sets.”15 

The Court rejected the construction the Department sought citing to the public policy of the FOIA regarding open and accessible public records. The Court concluded that information in the Cancer Registry “tends to lead to the identity” of Cancer Registry patients only if that information can be used by the “general public to make those identifications.”16 Further, the Court discussed the fact that the Department’s expert had years of experience, specific knowledge of data systems and the ability to adeptly manipulate data; but, her testimony failed to establish that the general public could recreate what she accomplished. And, the Department did not adduce competent evidence of whether a non-expert could perform the procedure followed by its expert to identify Cancer Registry patients.17 Dr. Sweeney’s conclusion that the general public could identify Cancer Registry patients was not supported by proof.18 Rather, the Court concluded that Dr. Sweeney’s testimony supports the determination that her methodology was unique to her education, training and experience, and not easily duplicated by the general public.19 

Further, the Court noted that the Department did not demonstrate that the release of the Cancer Registry information requested by Plaintiff “tended to lead to the identity of the specific persons described in the data” and as such did not meet the burden under FOIA to establish that the requested material was exempt. Finding that in the absence of more definitive proof that members of the general public would have the ability to duplicate Dr. Sweeney’s multi-step experiment, the Court relied on public policy to guide its analysis. The FOIA “encourages a free flow and disclosure of information between government and the people” and it is to be interpreted liberally, and the exemptions interpreted narrowly.20 

Based on this analysis, the Court upheld the trial court’s order instructing the Department to disclose the information in the FOIA request.21 


The Southern Illinoisan case reaffirms that courts hold public policy considerations in high regard when reviewing FOIA cases. Also, when exemptions are applied that look at the ability to identify the exempted information, the determination will be based on the general public’s ability . . . not that of an expert.

Lisle A. Stalter is an Assistant State’s Attorney in the Lake County State’s Attorney’s Office, Waukegan, Illinois. She is a member of the ISBA Assembly, Government Lawyer Committee and Secretary of the Environmental Law Section Council. The opinions expressed herein are solely those of the author and are not those of the Lake County State’s Attorney’s Office.

1. Southern Illinoisan v. Illinois Department of Public Health, No. 98712, 2006 Ill. LEXIS 309 (Ill. Feb. 2, 2006).

2. 5 ILCS 140/1 et seq.

3. 5 ILCS 140/7(1).

4. 410 ILCS 525/1 et seq.

5. Southern Illinoisan, No. 98712 at 2, 2006 Ill. LEXIS 309 at *2.

6. Id., No. 98712 at 3, 2006 Ill. LEXIS 309 at *3. 

7. Id., No. 98712 at 3, 2006 Ill. LEXIS 309 at *4.

8. Id., No. 98712 at 15, 2006 Ill. LEXIS 309 at *29 (citations omitted).

9. Subsequent to the filing of the Complaint in this case, the legislature amended Section 4(d) of the Registry Act. The amendment listed facts that lead to the identity of a person, including: “name, social security number, address, and any other data element that, by itself or in combination with one or more other data elements, tends to identify any person” (as amended by P.A. 90-607, § 20, eff. June 30, 1998). The Court determined that the analysis was the same under either version of the Registry Act. Id., No. 98712 at 24 - 25, 2006 Ill. LEXIS 309 at *47 - 48.

10. 5 ILCS 140/7(1)(a).

11. Southern Illinoisan, No. 98712 at 9, 2006 Ill. LEXIS 309 at *16. Dr. Sweeney holds an undergraduate degree in computer science from Harvard University, a master’s degree in computer science and electrical engineering from MIT and a Ph.D. in computer science from MIT. Id. 

12. Id., No. 98712 at 9, 2006 Ill. LEXIS 309 at *17. 

13. Id., No. 98712 at 17, 2006 Ill. LEXIS 309 at *32.

14. Plaintiff’s request for documentation specifically referred to documents relating to the incidence of neuroblastoma. Neuroblastoma is a cancer of the peripheral nervous system typically developing in infants and young children. Id., No. 98712 at 2, 2006 Ill. LEXIS 309 at *2.

15. Id., No. 98712 at 12, 2006 Ill. LEXIS 309 at *21.

16. Id., No. 98712 at 28, 2006 Ill. LEXIS 309 at *55.

17. Id. 

18. Id. 

19. Id, No. 98712 at 28 - 29, 2006 Ill. LEXIS 309 at *56. 

20. Id., No. 98712 at 30 - 31, 2006 Ill. LEXIS 309 at *59 - 60.

21. Id. No. 98712 at 31, 2006 Ill. LEXIS 309 at *60.

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