What is the process for retroactively (post completion) reviewing plagiarism on a dissertation? I am currently at a community college so I am not privy to the inner workings of the big university world but I am curious how this works. 

Recently it has become headline news that a student from a prestigious Ivy League school apparently completed their PhD back in 2000 with a dissertation that contains significant amounts of plagiarism. The university has supposedly initiated a review (though they are officially taking the standard "no comment" position and also the more extreme position of not even confirming if they are conducting any investigation). 


  Note: Here is a link to the news article for those interested in the details but I do not want to make this Question all about the politics involved, I am interested the academia processes. 


At first glance I was rather stunned that a school as prestigious as this one could have possibly accepted such extremely poor work and provided a PhD based on it but I guess even the best of us can make errors. What I want to know now is how such "fixing past mistakes" issues are typically handled.

Specifically I would like to know the following (based on your experience at your institutions):

(1) Would such a review process be limited to the dissertation itself or would all the work of the student be reviewed?

(2) Would such a review involve questioning the academic advisor/research supervisor? What about the thesis committee? 


(2a) On a sidenote: Would the thesis committee for a doctorate degree be obligated to check the research in detail or are they allowed to rely on the research supervisor for that task? 


(3) Would such a review look at the theses of other PhD graduates who were under the same supervisor? 

(4) What happens if such a review finds a doctorate is academically or ethically flawed? What, if any, penalties can be invoked against the student?

(5) If the outcome is to void the degree would the student be offered a chance to comment/defend or would the degree be revoked without warning? 

(6) How long would such a review typically take to complete?

Because this Question is prompted by a high-profile incident I am not sure if any of the process used by Columbia University in this particular case will be "typical". For instance I can easily envision that some eager beaver investigative reporter will pull copies of all the theses with the same supervisor and look for more instances of plagiarism. If I can predict this I am just as sure that Columbia will do the same and want to get ahead of any exposé by both expediting the initial review and being comprehensive to prevent any further "unexpected" embarrassments. 

That said, I would like to know what is/has been typical in such review processes before today.
The scenario of an investigation for suspected plagiarism in a PhD thesis is so rare and unusual that I'm pretty sure there is no "typical" recipe for how it would unfold. However, I'm familiar with one such case that happened some years ago at my institution, and I'll take that case as my definition of what "typically" happens.


  (1) Would such a review process be limited to the dissertation itself or would all the work of the student be reviewed?


It might, if the student's other work was available to be inspected (which I think is doubtful since the student will have already graduated), and if there was some concrete basis for suspecting plagiarism in that work, and (which IMO is the least likely condition to be satisfied) if the people involved in the investiation had enough time on their hands and were energetic enough to pursue such secondary investigation leads.


  (2) Would such a review involve questioning the academic advisor/research supervisor? What about the thesis committee?


This would be highly embarrassing to the people you are mentioning, so I expect they would only be questioned if there was a strong basis for believing that the information they could provide would materially affect the outcome of the investigation. Thus, the advisor might be questioned to get some background information on what took place when the student was writing the dissertation; the thesis committee members, almost certainly not.


  (2a) On a sidenote: Would the thesis committee for a doctorate degree be obligated to check the research in detail or are they allowed to rely on the research supervisor for that task?


See the comment by BrianDHall. The thesis committee never "checks the research in detail", and in all except a rare handful of cases, neither does the research supervisor.


  (3) Would such a review look at the theses of other PhD graduates who were under the same supervisor?


This question suggests to me that you have watched one too many episodes of late-night TV crime shows. Unlike such shows, universities aren't populated by dogged investigators (with checkered pasts and colorful personalities, usually divorced and heavy drinkers) who work day and night, dedicating their lives to exposing all instances of wrongdoing and then bringing the perpetrators to justice.

In other words, the answer is no.


  (4) What happens if such a review finds a doctorate is academically or ethically flawed? What, if any, penalties can be invoked against the student?


Given that the student has already graduated and is no longer a member of the campus community, the only punishment the university can actually impose is to revoke the degree. The only real question to debate would be whether the student would be allowed to come back and rewrite the dissertation if they wished to. Moreover, given the severity of the offense, and the risk posed to the university's reputation and credibility by PhD degrees it grants that are based on plagiarism, revoking the degree seems like a completely appopriate and logical response.


  (5) If the outcome is to void the degree would the student be offered a chance to comment/defend or would the degree be revoked without warning?


Undoubtedly the student would be given a chance to defend themselves against such an accusation before any action such as revoking the degree is taken. They would likely be entitled to ask for the case to be reviewed by a committee, and to have a panel convened where they could present evidence in their defense. Given the high stakes involved, if they wished to contest the accusation they would likely hire an attorney.


  (6) How long would such a review typically take to complete?


Probably a few months, but I assume it can vary a lot and take longer in some cases or be completed quite quickly in other cases.