how to find water leak inside lexus

One of the common issues where we had leaks on RX350's were actually from the back hatch support brackets. The body leaks and the carpet can be wet from the back all the way to the front. Not saying thats what it is but it's a possibility. Sunroof drains run through the rocker panels, maybe a tube is pinched or broken and is draining inside and not out? Ive seen in high humidity situations the evaporator core drain bein clogged and water backing up and running out of the case all over the floor on both sides.