The student at my university was expelled for plagiarising another student's work. He used snippets of the other student's paper, oblivious to how easy this is to check. He had also failed to reference many of his sources properly, which further added to the damage.
When students hand in their papers, the papers are checked against an automatic plagiarising detection program which sources the references in their biographies and checks against the corresponding paper. If you are over a certain percentage, you will either: fail the assignment; the whole subject; or be expelled depending on the percentage level of misconduct.