Referencing is a key part of the startup hiring process and recruiters should state their practices clearly. Referee names must be supplied early in the process, and no-one approached unless the candidate gives their permission.
The most scrupulous interview process still only demonstrates a candidate's capacity to perform convincingly in that environment. In order to identify skills gaps or potential problems, there are several ways to follow up references. Call the candidate's former colleagues (discreetly) to collect critical information not included in a formal reference, such as how the candidate performs in a live working environment. Referees should include a former manager, direct superior and peer worker, and if candidates are reluctant to supply any one of those, it could flag a potential problem.
The purpose of reference calls is to uncover new information, and the caller must have the confidence to probe, direct and redirect a conversation to reach it. This person will have been involved in the interview process from the outset, and have a clear idea of what areas of obscurity or potential problems need to be clarified.
Skilled questioning is vital, as the referee's answers may redirect the caller's questions. Such calls can only be navigated by someone very familiar with the candidate and their background, as the most important information often won't be explicit. Referees are prone to avoid difficult topics and soften any criticism in case of repercussions, so the key element to look for is pattern recognition. Overly negative or positive references suggest that the referee is judging on a personal relationship rather than with a professional view.
Ask only questions that can be answered easily in a few brief sentences. If an answer seems unclear or ambiguous, ask again and clarify what answer you're seeking. If the referee is still vague or evasive, make a note and come back to it later. Look for anecdotal evidence to back up any information supplied.
Informal references can steer your formal interview questions and can be sought even before the candidature is confirmed. Ideas developed during the process can be pursued, perhaps by investigating shared connections in a common network. Particular care must be given here, as the candidate's current situation must not be compromised, or their candidature revealed to anyone in their present company. Be sure, before contacting any person for their views on the candidate, that it won't impede or derail the recruitment.
If possible, make it appear that the candidate has not yet been contacted and suggest that their opinion is being sought before any formal approach. Questions should also be delicately phrased, so that the referee has some context. Outline the candidate's prospective role and ask if the referee thinks contacting the candidate would be a good idea. In either case, make sure the referee's answers are clearly understood, that their responses are candid (or not) and push for answers accordingly.