I'm wondering how a proctor of a closed-book exam should approach the case where a student has a tattoo that would double as a cheat sheet. Maybe they think the math looks cool, or they got a nice calligraphy of a textbook passage, or they are just that desperate to cheat.
Now, on one hand, that tattoo is pretty much a permanent fixture. On the other hand, that is a cheat sheet written on your forearm. In fact, it might be a particularly brazen attempt at cheating. And on the gripping hand, the fact that a resource is available for easy reference whenever needed doesn't carry much weight in the context of a closed-book exam.
At least in my university, the general rule for exams is "No written material unless expressly permitted", and most of the exams that permit bringing a "cheat sheet" have had a restriction on the sheet size (e.g. one-sided hand-written A4 paper). Therefore, a situation may well arise that a student shows up for an exam with the maximum-sized cheat sheet, and some related math (purportedly) tattooed on their forearm. If I find myself proctoring an exam and this happens, how should I approach the situation?
This is an entirely hypothetical question so far, so I'm unable to provide details of a real-life example.