A quick way to judge this (though not always correct, since there are too many other factors to judge before a decision) is to focus on whether the expert sounds a know-it-all, whether he/she sounds arrogant, and whether he/she is habituated to working as a lone wolf.
If so, and you determine the expert still has sufficient expertise to contribute positively - it might be helpful to hire him as an external consultant rather than as an internal full-time employee.
Does the candidate sound arrogant?
There is an important distinction between demonstrating competence in an interview and sounding arrogant.
The interview is a place for candidates to discuss their special talents and skills. However, when a candidate explains past situations or behaviors in an arrogant tone - they are actually trying to impress upon you their superior importance.
They are communicating that they feel they are entitled to greater rights than others or that they are of greater value than others - and often, these others can be past employers, colleagues or subordinates.
You don't want something like that inside your organization.
But there's little issue in having the same person as an external consultant providing solutions from outside your internal hierarchy.
Is the candidate habituated to working alone?
Usually, standard interview structures are sufficient to give an insight into whether a candidate would perform well as a team member. If the job position requires performing as a team member, then listen carefully for cues to find out whether the candidate likes working all alone or with others. Keep in mind that "teamwork" is a well-known buzzword and many would insist they are team players. Look for evidence, ask about preferences and try to nail whether the person genuinely likes working in a team, or working by himself.
Is the candidate a "know-it-all?"
This is a place where many recruiters slip while hiring top professionals. A domain expert is supposed to know more than others; that's why the person is being recruited - but no one is supposed to know everything there is to know, about whatever comes along.
An interview requires that the interviewer asks questions and the candidate answers them.
However, the manner in which the candidate delivers the answers is critical. If the candidate is always projecting himself as an authority - that can indicate problems.
If he always has the answers, and coworkers always failed to come up with solutions - that is big problem.
You would want in-house experts to be facilitators.
People who are unable to say "I don't know" and unable to ask "What do you think?" are unable to start movements and collaborations.
However, they might still be excellent individual contributors as their egos make sure of high quality benchmarks and professional integrity in delivering services.
Excellent as an external consultant - risky in-house.
