Kerr 3 Orin S. Kerr, Associate Professor, George Washington University Law School. Northwestern University Law Review Winter, 2003 97 Nw. U.L. Rev. 607 ARTICLE: INTERNET SURVEILLANCE LAW AFTER THE USA PATRIOT ACT: THE BIG BROTHER THAT ISN'T lexis
The law often distinguishes between prospective and retrospective surveillance because they raise somewhat different privacy concerns. As Justice Douglas noted in his concurrence in Berger v. New York, n38 prospective surveillance can at worst constitute "a dragnet, sweeping in all conversation within its scope." n39 The surveilling party taps into the network at a given location and picks up traffic passing through, but cannot know in advance exactly what the traffic will be. Some of the traffic may prove relevant, but usually much of the traffic will not be. n40 Further, it can be technically difficult (if not impossible) to filter the communications down to the relevant evidence before the government observes it. Accordingly, prospective surveillance tends to raise difficult questions of how the communications should be filtered down to the evidence the government seeks. n41 In contrast, the scope of retrospective surveillance is generally more limited. The [*617] primary difference is that in most cases a substantial portion of the evidence will no longer exist. n42 Because retrospective surveillance involves accessing records that have been retained in a network, the scope of surveillance ordinarily will be limited to whatever information or records may have been retained in the ordinary course of business. n43 Some records may be kept, but others may not.
