I don’t think the interviews have to be fully carried by juniors. You’re right, a junior interviewer will not be able to ask the right followups or have the experience to dig deeper into the answers the candidate is giving. Nonetheless, I found that when you perform technical interviews it is actually possible to get a signal on whether you might be hiring jerks or people that might be a liability. For example, take a female software engineer and a male manager to do the technical interview. The female engineer is the one that asks majority of the questions, and the manager only jumps in once in a while. Then watch out for cues where the candidate gives more attention to the manager, instead of the person who is leading the interview.