Which logical fallacy is used in the text?
I don't trust Professor Stewart's findings. Another researcher at her university was caught falsifying data. So, it's likely Professor Stewart has, too.

 - circular reasoning: an argument that supports a claim with the claim itself
 - slippery slope fallacy: the false assumption that a small first step will lead to extreme consequences
 - guilt by association: a negative association intended to discredit someone or something
The text argues that Professor Stewart's research is untrustworthy because someone else at her university was caught falsifying data. However, this isn't necessarily true. The practices of one researcher at a university do not necessarily reflect the practices of another researcher at the same university. This illustrates a type of logical fallacy known as guilt by association.