If you are getting proxy/fake interviewees, there are deeper problems in your process than evaluating who is under the hijab. If people are trying this, it means you are conducting business in a way that makes it profitable to provide proxy/fake interviewees.
It sounds like you need to look at how you are managing contractors.
Responsibility for Results
If whoever you contract with has payment tied to results, then there is no incentive to provide fake/proxy interviewees. If person A proxy interviews because they can convince you they can do the job, but then person B is hired to really do it, there can be three results:
- Person B does the job fine, and there is no problem
- Person B doesn't do the job fine, and doesn't get paid
- Person B doesn't do the job fine, and does get paid
The only incentive to going through the hassle of dealing with proxy interviewers is if the third result is a possibility. Tying payment to results makes sure that there is no incentive to make a bait and switch.
Reliability of Contractors
If you are worried about fake/proxy interviewers, you must not have much faith in your contracts. After all, the contract should outline:
- Work to be done
- Parties to do it
- Whether subcontracting is allowed
- Who will be paid how much
- What penalties there are for breaking it
If subcontracting is allowed, it doesn't matter if the person you interview is actually going to be doing the work. If subcontracting isn't allowed, but you are concerned they will do it anyway, how can you trust that any other part of the contract will be followed either?
You should make sure that you are working with a reliable contractor who you trust to actually follow the contract, as a reliable contractor will be far more likely to accept a contract that ties payment to results. If payment is tied to results, in the worst case you don't get the work done, and you don't pay the contractor.
If the work is so critical that outcome is unacceptable, why are you outsourcing in the first place?
If you handle the previous two, the issue of identifying the person in the interview should be far less significant (since the person on the contract is the one who is responsible for results, and the one that will/won't get paid regardless of who you interview with). However, you may be concerned that if you get a resume from Jane Doe with experience X, Y, Z, that the person you are actually speaking to is the same Jane Doe.
Run a background check. Ask the person about the results of that background check. Ask them to show a state-issued ID (passport, national identification card, etc.) that verifies the details the background check digs up. If someone is so good at proxy interviewing that they prepare the other person's state-issued ID, memorizes their academic record, birth date, past employment, etc. then there really isn't going to be any way to effectively make sure that they are the same person in the first place.
Again, this is really a last-resort sort of thing, because a proper employer-contractor relationship will have disincentivzed fraud through the contract itself. If you can't trust the contract, then you shouldn't be using contractors in the first place for anything that you need to worry that much about.