I have recently been involved in a case where the argument came to one of who is an expert. This is not an uncommon attack when the issues at hand are not really in dispute and the opposing team wants to focus the case on other things. It may seem strange that a person with multiple post graduate degrees, SANS/GIAC certifications (and others) up the wazzoo and years of experience can be challenged on these grounds, but it is not unusual in this industry.