How do I interview someone more experienced than me?

Decision quality, which is visible to anyone who listens carefully. Ask about a hard call they made, then work through it: what options were on the table, what they rejected and why, what they got wrong, and how they would approach it now. Strong senior people explain trade-offs in plain language and volunteer the weaknesses of the path they chose. Weaker ones describe outcomes without decisions, or cannot say what would have changed their mind. You can also assess how they handle being questioned by someone junior, which is directly relevant if they will work with your team. None of that requires you to know their domain. Ask what they would need from a company to do the job well, since the answer tells you whether it is workable here.

Do more preparation than usual and let structure carry you. Read their background properly and write your questions down in advance, including the follow-ups. Agree with the hiring manager which competencies this round owns so you are not attempting a general assessment of a career longer than your own. Prepare two or three specific scenarios from your actual environment and ask how they would approach them, since that reveals fit with your context rather than testing recall. Know the answers you would consider strong before you start. A well-prepared structured interview makes the seniority gap largely irrelevant, because the questions do the work. Rehearse the opening once if it helps, because a settled first two minutes carries the rest of the conversation.

For technical depth, yes. Pair yourself with a senior practitioner or an external adviser who can probe the craft, and keep your own round focused on what you can genuinely evaluate: collaboration, communication, motivation, how they operate with the people around them. Splitting the loop this way is normal and it is honest. What does not work is one person attempting to cover everything and quietly deferring to the candidate's confidence throughout. If your company has nobody senior enough in that discipline, bring in a trusted external practitioner for one round. Assign competencies to interviewers explicitly in your applicant tracking system so the coverage gap is visible rather than assumed.

By being straightforward about your role and running the process properly. Say who you are, what this round covers, and how the decision gets made. You are not pretending to be their peer, you are assessing a specific set of things and representing the company. Do not bluff on technical points, since experienced candidates spot it immediately and it costs you their respect. Asking someone to explain a concept in more detail is a strength, not a weakness, and how they explain it is itself evidence. Keep to time, close cleanly, and follow up when you said you would. Senior candidates judge companies heavily on process discipline, and that judgement is often what decides whether they continue.