I've been tasked with interviewing several offshore consultants in sequence for proper job skills, and given a short amount of time to prepare. I've got 6 candidates to interview. I get a half hour per interview. The call is monitored by an onshore consultant who is coordinating the call, and an offshore consultant monitoring from their end.
I have no way to assure these candidates aren't sitting near each other by the phone, answering questions while on mute between my questions. No video.
I use a series of 12 basic technical skill questions that are obfuscated enough that they might not get targeted in an online search, and I have 2 follow-up tests (generalized as (1) is there a problem with this code sequence and (2) investigate this error trace for me) that I e-mail out directly to the interviewee.
I start interviews by asking technical questions about their prior experiences per the information listed on their resumes. Then I try to get them to answer any of my 12 questions by framing them through that prior experience. The 12 questions are in a sequence of increasing difficulty, which I only break based on application to prior experience. I finish with asking outright any of the 12 questions that haven't been answered, and follow-up with walking through the e-mailed questions, with phone-based (non-typed) answers.
I feel I cannot customize the e-mail-based questions on a per-candidate basis to my satisfaction, and I will, but prefer not to, add additional, brand new, qualifying questions. And yes, I do realize that I took some of the increasingly short time I have to put together new material to write (and edit) this question.
How can I best qualify these offshore consultants?