What do I do about the order of a workplace investigation?

To plan my investigation, unless there are logistical issues, we always do the reporting party first and the accused last. Aside from that, sometimes we'll interview someone just because we need to learn the subject. So, for example, if I needed to know about an accounting practice or how chemicals reacted to cause some part of a workflow, I might interview someone pretty close to the beginning, just so I can understand that material I'm unfamiliar with. But otherwise, generally speaking, I work it out where people's schedules interfere the least with what they're doing to serve the organization in the first place, and try to focus on people who are managers usually or who have a vast scope of information towards the end, so that I can corroborate all the little pieces that I've learned along the way, right before I interviewed my accused.