As people readers it is our job to pull the bad and keep the good. It's not to say that one or two won't slip by us, I sure have had my share that have. It is our job to eliminate the risk, if you are unsure it is better to pass that person on and let the next person know what your reservations are. If you don't want to "taint" the interview with your perception after the hiring manager interviews the candidate, ask about the areas you were unsure about, discuss them, and make the decision together. If you keep your thoughts to yourself and the person is hired and find out about issues with the candidate, you'll be walking around the office for months saying to yourself "I knew it". Knowing it means nothing when you did not do something about it.

Hiring is a decision made by all parties and you have to work together to find the right candidate, for the right position, at the right time. Your instinct as a recruiter plays a big part of that. Use it and if you are unsure, follow-through. Don't second guess yourself.