"The fact finding process is consistently defined to include evaluations of credibility and demeanor. Research on video-mediated communications strongly suggests that videoconferencing prevents the accurate assessment of customary indices of these characteristics. Therefore, videoconferencing fails as a fact finding method in contexts such as immigration courts where determinations rely heavily on observational assessments of credibility." Harvard Law Review, Feb. 2009, pp. 1181-1193.
http://www.harvardlawreview.org/issues/122/feb09/DEVO/DEVO_intro09.pdf