I am nearing the end of teaching a course for first year students with a fellow student.
We assigned a paper and 2 students have submitted almost identical papers. The policy is that if a student is caught they get a 0 and possible legal action on a case-by-case basis governed by department heads.
I know that one of these students is a 4.0 students and it seems odd that she would either share or copy her paper from another student. I'll refer to her as student A. Student B's paper is about a 90% copy and normally cases where this happened it's evident that the students are friends and socialize during classes. I have never seen Student A and B talk to one another and I find it hard to believe student A would plagiarize off of another student.
I do not want to have to fail both students if only 1 copied off the other without the other's knowledge. How can I appropriately handle the situation without seeming like there is a favoritism towards student A? Student B has been on the lower end of the class grade wise but is still a passing student.