Internal vs External Examiner: The Roles in a PhD Viva (and the US Committee Equivalent)

What each examiner is actually responsible for

In the standard UK PhD viva, two examiners read your thesis and conduct the oral examination together. Their responsibilities are not symmetrical.

• The external examiner is appointed from another institution. They must be a senior academic with genuine expertise in your field and no prior involvement with your project — no supervision, no collaboration, no co-authorship. Their role is to provide an independent, nationally-comparable assessment of whether the work meets doctoral standard. At most UK universities, the external formally leads the oral examination.
• The internal examiner is a member of staff at your own institution, usually from your department or a closely related one. They handle the administrative arrangements (booking the room, completing the paperwork, relaying the outcome to your supervisor), help ensure the examination follows university regulations, and question you alongside the external. After the viva, the internal typically checks that any minor corrections have been completed.
• Both examiners are expected to read and independently assess the thesis before meeting on the day. At many universities they exchange preliminary reports on the morning of the viva, having not seen each other's view beforehand.

Who leads the questioning — and who has the final say

The external examiner conventionally leads the viva. In practice this usually means they open the examination, set the pace, and ask the majority of the questions — often around 60% by most candidates' accounts. The internal examiner questions you throughout, typically at points the external invites, and may press particular areas where the institution's own standards or context are relevant.

Neither examiner has a unilateral veto. The outcome is a joint recommendation. If both examiners cannot reach agreement, the doctoral college must be notified — a situation that is uncommon in practice but provided for in regulations at every major UK institution. Where the examiners do disagree, the external's view tends to carry more weight by convention, precisely because they are the independent assessor. But formal regulations at universities such as Manchester, Nottingham, Warwick, and Leeds frame the outcome as a joint decision, not one examiner overruling the other.

The examiner's joint written report, completed after the viva, sets out the recommendation and — if corrections are required — the specific changes the candidate must make. In the UK the possible outcomes range from an unconditional pass to minor corrections, major corrections, revise and resubmit, referral for a lower degree, or fail. Minor and major corrections are the most common results for first-submission theses.

The US and European model: committees, not pairs

The internal/external pair is specific to the UK, Ireland, and parts of the Commonwealth. In the United States, the examination is conducted by a dissertation committee, typically four or five faculty members, and the structure is different in three meaningful ways.

• The committee usually includes your advisor. In the UK, your supervisor is explicitly excluded from the examining panel — their job was to get you to submission, not to assess it. In the US, the advisor is typically the committee chair and is present throughout.
• There is no single 'external examiner' in the UK sense. A US committee may include one or two faculty from outside your home department or occasionally from another institution, but they are not playing the same independent-assessor role. Their involvement has often been continuous throughout the PhD rather than beginning at the point of examination.
• US defenses usually open with a public presentation — typically 20 to 45 minutes — before the committee questions the candidate in a closed session. There is no equivalent presentation requirement in a standard UK viva.

Most European systems sit somewhere between the two. Germany and the Netherlands, for instance, use committees, though their composition and the weight given to different members varies by institution. Australia has traditionally examined through written reports from external examiners rather than an oral, though oral components have become more common in recent years. If you are examining or being examined outside the UK and US, your institution's regulations are the only reliable guide.

Preparing for two examiners with different interests

The external examiner is assessing your work against national doctoral standards and the state of your field. They will probe your contribution, your command of the literature, and the reasoning behind your methodological choices. They are not invested in your success — they arrived with no prior relationship to the project. Expect field-level questions: where does this sit in relation to the three most-cited papers in your area? What would your critics say? Why this method and not the obvious alternative?

The internal examiner knows your institution's specific requirements and often knows your department's conventions. Their questions tend towards process and clarity: are your claims proportionate to your evidence, are your chapters internally consistent, are the corrections from your upgrade accounted for? This is not necessarily gentler — an internal who spots a methodological inconsistency will press on it — but the frame is different.

Practically: read your external examiner's recent publications before the viva. Understand where their work intersects with yours. If they have written critically about the methodology you used, know how you would respond. Your internal is worth speaking to beforehand about the likely shape of the examination and any process-level concerns about your thesis.

In a US defense, the preparation logic is somewhat different because your committee already knows your project. The challenge there is showing independent command — that you can step outside the work and assess it, not just describe it. Rehearsing with someone who hasn't read your thesis is one of the more useful things you can do.