Welcome SwampThing.
Maybe what's happening with your friend has to do with matters other than the jw religion. For someone to turn to a pattern of lying seems odd, jw or not. The religion does not condone lying in everyday dealings (though many jws do it anyway). Maybe your friend is lying to cover something up, and hence, since more lies are needed to keep up the original.....
Maybe there's a personal, physical, or marital problem that's behind his abnormal behavior. Or, maybe it does have something to ddo with the religion. It certainly exerts a great pressure in the lives of its adherents. Maybe he cracked under it, which happens often in dubdom (I'll throw in another term unique to the jws).