Here's one thing i've learned to help me distinguish a control from a relevant question... this is for a pre-employment poly with direct-lie questioning:
Ask yourself if this: would have a 'desirable' applicant done this? ie. stolen from an employer (most people have stolen minor things)... driven after drinking (any amount)... committed an undetected crime.  These are all controls.
When the seriousness of the questions increase, ie. a serious crime is defined, stolen something in particular or a large amount of money or mercc, it becomes relevant.