What qualifications make up an Expert?

The law doesn't confirm to logic or reason - so I wouldn't use that as an example :-)I would echo what others are saying - what is the standing of the person with their peers? How do we judge this ?How often their peer-reviewed work is cited in other peer-reviewed work seem to work quite well for me as a measure.Be very wary of people who provide "evidence" via websites or Verbal means.