Has/had handled. It depends on the starting point of reference. If you are "in the present" time, use has had. If your reference point is in the past, use had handled.
The person still works with me who handles such queries though he hasn't dealt with such queries lately.Now I have to report to someone about that because I'm getting lots of queries to be addressed in which he has the expertise. So, it means point of reference is present.It implies I use HAS.Is that right?