Seattle - The investigations being conducted by copyright holders on file-sharing networks to discover instances of infringement are flawed, and can mistakenly identify innocent parties, according to a new study from researchers at the University of Washington. The researchers monitored file-sharing activity on the BitTorrent network last year, and in the course of their study received 206 complaints of infringement under the Digital Millennium Copyright Act (DMCA) -- even though their machines transferred no illegal files.