Thoughts on Academic Tenure by Joseph F. Baugher (August 15, 2014):
Tenure can only be revoked for valid cause--normally a professor has
to do something really wrong or really stupid to lose tenure. Most
universities have disciplinary procedures already in place for
handling such cases—typically a quasi-judicicial proceeding is
provided, surrounded by due-process protections and an opportunity for
the accused to provide a defense. Such cases are quite rare--in the
US, according to the Wall Street Journal (Jan 10, 2005), it is
estimated that only 50 to 75 tenured professors (out of about 280,000)
lose their tenure each year. Revocation of tenure is usually a
lengthy, costly, and tedious procedure, very often resulting in a
lawsuit. Grounds for dismissal typically include doing something
illegal like embezzling research funds, stealing school property, or
conviction of a felony or any offense involving “moral turpitude”.
The grounds for tenure revocation can also include things such as
professional incompetence, gross academic malfeasance such as
plagiarism or the faking of research results, falsification of records
or credentials, neglect of duty, unprofessional or confrontational
conduct toward colleagues, sleeping with a student, sexual harassment
of another faculty member, or other conduct which falls below minimum
standards of professional integrity. A tenured faculty member can
also be dismissed if they develop a physical or mental disability, one
so serious that even with reasonable accommodations the faculty member
is no longer able to perform the essential duties of their position.
Carolyn J. Mooney, "Dismissals for Cause", The Chronicle of Higher Education, December 7, 1994, p. A17, as reported by Wikipedia:
In 1994, a study in The Chronicle of Higher Education found that
"about 50 tenured professors [in the US] are dismissed each year for
cause."