If you believe you have identified a potential case of scientific misconduct, there are a number of steps you should take to resolve the matter. First, you should informally discuss the matter with a faculty member you know, such as your thesis advisor or member of your thesis committee. Such discussions may help define the problem, put it in perspective, and help you decide whether further steps are warranted.
If you believe the matter requires official notice, the next level of discussion is at the departmental level involving either the Director of Graduate Studies or the Chairman. The department takes these matters seriously, and will not penalize an individual for raising reasonable concerns. All steps will be taken to preserve confidentiality to safeguard all parties involved in the dispute.
For more information, please visit http://catalog.yale.edu/gsas/policies-regulations/