The problems surrounding "free and informed consent" are discussed in this article by Dr. May, who is Professor of Religion in the Department of Religion and Religious Education at the Catholic University of America.
May, William E.
"Experimenting on Human Subiects,"
The Linacre Quarterly:
4, Article 4.
Available at: http://epublications.marquette.edu/lnq/vol41/iss4/4