take it up with flt safety
Rajesh,
Seems like you might have something in this after all. I suggest you talk to your flight safety team , you have a line pilot/flight safety representative for each of the fleet. Talk to them about your concerns . Worst case, they check it out and you get egg on your face , but you can sleep easy .It's a tough call but it could be his knowledge , behavior , conduct,attitude gave you the red signal about his history.
There's nothing worse than sitting on your hands when you know something is amiss. I don't care if a faker is brown, white, yellow, black ...indian , pakistani, american or whatever...a faker needs to be caught, period.
All the best, masalama.