It's so that they can figure out why the process wasn't being followed and how it can be improved. Nothing is perfect and accidents are a great catalyst for reexamining your procedures.

What could change to make it more likely that the process would be followed? Could we put signs all around places with prion research? Could we implement a buddy system whenever we work with prions? Do metal gloves need to be hung in visible place throughout the lab? Do we keep containers of bleach accessible for when someone pricks their finger? Do we have enough of them and are they visible enough?

Part of a process audit is to check compliance, e.g. by counting if there are enough metal gloves per employee - including measuring all hand sizes to check if really every employee even has access to a fitting glove -, by checking if supply orders for PPE match expected consumption, by interviewing current and especially former employees and by checking emails for evidence of staff complaints.

She hadn't been trained in how to handle prions. Doesn't that sound like a process problem to you?

Someone not following a process is a failure of the process. The process should include proper training and regular oversight to ensure that the process is being followed - an audit will reveal if that training and oversight is in place. If you trace any accident back far enough, you'll eventually get to a point where it could've been prevented with better planning.

if we have some dangerous prion, and some person is bypassing procedure, that still is needing some evaluation. prion escape and becoming common in populations would be a large disaster.