I ask myself whether this problem is also part of the US mentality: in Germany, one would rather be tempted to treat even white lies as fraud, and thus compare (culturally, though not legally) such liars with criminals.
On the other hand, in my experience such fraudsters are in most cases easy to detect: just ask them some hard questions (where the candidate will either know the answer or not, thus rhetorics or charisma won't help) about the topics that the candidate claims to have expertise in (choose the question in a way that even very capable candidates will only be able to answer a fraction of them - this is fine and intended).
Typically, after 30-45 minutes you are either sure that the candidate tells the truth about his capabilities or is a liar (hardly ever anything inbetween happens).