You’re interviewing someone for a position at your company. You remember working with that person years ago, and you were unimpressed. Maybe it was the jerk factor, maybe it was the way he didn’t quite finish work, or maybe it was her perfume. Whatever it was, you were not excited about the candidate then, and you would like to avoid working with the candidate in the future. What do you do?
Tell the hiring manager. Explain with examples. “Back 10 years ago, when the candidate and I worked at SmallerCo, I was unimpressed by these things.” (Explain the things. If it’s not finishing, explain what you thought done meant and what the candidate did.) “When you check references, can you please check on this?”
The hiring manager should then ask the references, “Can you give me an example of a time the candidate did a great job finishing something?” and “Can you give me an example of a time the candidate had trouble finishing work?” and “How often do you think the candidate was great at finishing and how often did the candidate have trouble?” (Change this question to be the issue concerning you.)
You should let your manager know about your reservations–that’s the unintentional reference part. But you should make allowances for people having changed over time.