Why do we conduct multiple interviews in the first place? Because, as a group, we want to gather all the information we need to make an informed decision. Some quick discussion between interviews can help make sure we gather all the information we need -- as long as you keep it to narrowly defined topics. In particular, I always try to find out: "What did you cover in your interview? What didn't you cover? Is there anything I need to know?"

Let's say we're interviewing someone for a role with HTML5, CSS, and JavaScript. If the first interviewer ran out of time before getting to JavaScript, I should probably start with that.

Or, if an interviewer noticed any red flags, we can use the following interviews to gather more information. If I was told that a candidate complained loudly about being overworked, then I could spend more time discussing time management and the way he works. Maybe he legitimately was overworked, or maybe he's a complainer, or not very good at prioritizing his work.

Finally, it helps if there's at least one recruiter or a manager that you can give real-time feedback. Recently I was on an interview loop of a candidate for a very specific role. I quickly realized she was a terrible fit for this position, but she'd actually be perfect for a different one. I went to our recruiter and explained the situation. He was able to reorganize the schedule so that the candidate spent the rest of the day interviewing for the right position. If we had just continued without any feedback, it would have wasted a lot of time and we would have missed out on a great candidate for the other role.