Except in some very specific circumstances an examiner must be qualified (and current) to fly as pic of any a/c in which (s)he is examining as well as being current as an examiner. For example, to legally examine in a Multiengine piston, you will have taken a (MEP) LPC within the last 15 months. So the examiner will be as current as any 'normal' pilot on the class or type.