Possible Clues:

• They know when you're telling the truth (2 words)
• The make-up artists set them off presumably, as they recognise a good yarn when they hear it
• Polygraphs
• Readers of stories?
• Polygraphs (2 words)
• They recognise a good yarn when they hear it ignoring the veracity of the facts
• Opens 14 across for sensitive types, as they can tell if things are not as you say they are
• Spotters on golf courses perhaps can tell if things are as you say they are
• They reveal specialists in invention?
• Spotters on golf courses perhaps can tell if you're telling the truth