What should a lecturer do when an international student plagiarises and the student claims it was unintentional? A student has plagiarised her assignment. The lecturer gave all students a lecture on plagiarism at the beginning of the semester. The student maintains she was absent that day but the university does not keep records on attendance. However a copy of the lecture is on BlackBoard. Her excuse is that she didn’t realise she was plagiarising.  As she is an overseas student a fail in a unit means she risks losing her visa.

What actions should the lecturer take?
If your institution keeps a record of academic misconduct, be sure this gets into the record.  If you don't do that, you enable serial cheating.

Do not allow a "do over."  The message you send is that there's no penalty for for misconduct, even if one gets caught.  Misconduct must have some irrecoverable penalty, however small.  It need not be a grade penalty; it could be extra work, but see below about setting a penalty.

Follow University policy if there is one.  If you have the opportunity to set the penalty, and I hope you do, consider the magnitude of the offense.  A single un-cited paragraph from a work listed in a bibliography is far less egregious than a substantial part of the work copied with no attempt at attribution.

It is not your problem that the student missed the plagiarism lecture.  Do not allow the student to make it your problem.

It is not your problem that the student might lose her visa.  Do not allow the student to make it your problem.