Tygar, a University of Berkeley professor of computer science and information management, told Judge Murray Wilcox that technology is the answer to keeping users from infringing on copyrights.
"There's extremely rapid progress being made in this area," he said. "For example, Windows now offers WMA format files that have something called Digital Rights Management. The digital rights management system makes it very difficult for users to exchange those files.
"Watermarking technology that's been developed can help assist in catching cases where infringement happens. I believe that the problem of copyright infringement is so pervasive in our society that legal mechanisms alone can never address this."
Wilcox admitted he had no idea as to the extent of use of thefor infringing copyrights.
"If somebody asked me tonight what is the proportion of infringing material compared to non-infringing I would have to say, I haven't got a clue," Wilcox said. "The evidence does not reveal that. I don't know whether it's 99.5 percent infringing or 0.45, I have no idea. This is part of the problem--that we know so little about it."
In his affidavit, Tygar said that it is generallyin the Kazaa system that the country the user specifies is actually the country in which the user is.
Kazaa distributes its Web pages using the Akamai server network. Akamai is a third party that distributes a wide variety of Web content.
According to Tygar, Akamai technology allows the creation of a list of IP addresses accessing a particular Web page or set of Web pages. He said that it is possible for Akamai to create a list of IP addresses of computers accessing Kazaa Web pages.
However, he believes that even if Akamai created such a list of IP addresses, Akamai has no way of knowing what files the Kazaa Media Desktop (KMD) users make available for uploading or what files KMD users download.
"For this reason, Akamai cannot know--and consequently cannot inform Sharman--whether its Kazaa Web pages are being accessed by users exchanging public domain files, copyright files with authorization, copyright files without authorization, or by users not uploading or downloading any files. Furthermore, a list of IP addresses would not yield information about end users," Tygar said.
Tygar added that Sharman's Web site plays no critical function in the file transfer. "As Sharman does not have access to any nodes or supernodes--other than those it might operate itself--the vast majority of file-sharing traffic occurs beyond its knowledge or control," he said.
He said that if Sharman were to cease to distribute the Kazaa application on its Web site, users could continue to obtain it through several methods.
"First, it is widely available on the Web. Second, it can be exchanged from user to user. From a technical standpoint, Sharman has no control over the distribution of these copies," Tygar said.
Wilcox has scheduled a special Saturday morning session to take evidence from visiting U.S. academic professor Keith Ross, who is testifying for Sharman Networks.
Kristyn Maslog-Levis of ZDNet Australia reported from Sydney.