The fourth category of methods that public libraries employ to enforce their Internet use policies, and the one that gives rise to this case, is the use of Internet filtering software.  According to the June 2000 Survey of Internet Access Management in Public Libraries, approximately 7% of libraries with public Internet access had mandated the use of blocking programs by adult patrons.  Some public libraries provide patrons with the option of using a blocking program, allowing patrons to decide whether to engage the program when they or their children access the Internet.  Other public libraries require their child patrons to use filtering software, but not their adult patrons.  Filtering software vendors sell their products on a subscription basis.  The cost of a subscription varies with the number of computers on which the filtering software will be used.  In 2001, the cost of the Cyber Patrol filtering software was $1,950 for 100 terminal licenses.  The Greenville County Library System pays $2,500 per year for the N2H2 filtering software, and a subscription to the Websense filter costs Westerville Public Library approximately $1,200 per year.  No evidence was presented on the cost of privacy screens, recessed monitors, and the tap-on-the-shoulder policy, relative to the costs of filtering software.  Nor did any of the libraries proffered by the government present any quantitative evidence on the relative effectiveness of use of privacy screens to prevent patrons from being unwillingly exposed to sexually explicit material, and the use of filters, discussed below.  No evidence was presented, for example, comparing the number of patron complaints in those libraries that have tried both methods.

The librarians who testified at trial whose libraries use Internet filtering software all provide methods by which their patrons may ask the library to unblock specific Web sites or pages.  Of these, only the Tacoma Public Library allows patrons to request that a URL be unblocked without providing any identifying information; Tacoma allows patrons to request a URL by sending an email from the Internet terminal that the patron is using that does not contain a return email address for the user.  David Biek, the head librarian at the Tacoma Library’s main branch, testified at trial that the library keeps records that would enable it to know which patrons made unblocking requests, but does not use that information to connect users with their requests.  Biek also testified that he periodically scans the library’s Internet use logs to search for:  (1) URLs that were erroneously blocked, so that he may unblock them; or (2) URLs that should have been blocked, but were not, in order to add them to a blocked category list.  In the course of scanning the use logs, Biek has also found what looked like attempts to access child pornography.  In two cases, he communicated his findings to law enforcement and turned over the logs in response to a subpoena.  At all events, it takes time for