Selecting the Best Freelance Human Factors Consultant, Ergonomics Consultant, or Usability Consultant

HFscout suggest using 3 main criteria for evaluating consultants:

1. Find consultants that match your project’s needs. In other words, search for consultants that have experience with your type product. Not experience using your type of product, but actually evaluating, testing, or designing your type of product. For example, don’t select a medical human factors professional with 20 years of experience in the field to perform usability testing on your Web 2.0 application just because they have been around for a long time. In short, the type of experience is, for the most part, more important than the amount of experience.
2. Interview consultants, and look for consultants that focus on end users (i.e., user or use centered design) and objective findings, not what they find pretty and or what they think is well designed. Graphic designers are easy to find and opinions should be free, but objectivity is what you should be looking for and buying. Remember, human factors is a science, and that is the quality that you should look for in a human factors consultant.
3. Look at the consultant’s educational background critically. Although someone can be a good self-taught practitioner, and someone with a Ph.D. can be a not-so-good practitioner, it is more likely that the consultants with formal education in human factors or a related discipline will be the better candidate in the end. And no, certification is NOT a substitute for a formal education. In fact, those with advanced degrees "...are the certified physicians of the field... [whereas a] Certified Usability Analyst program is aimed at designers and developers who want solid training for practical work in user-centered design. These are the certified paramedics of the field." [Reference]. For a freelance consultant, you probably want to hire the physician, and not the paramedic.