Pilot A signs for the aircraft; so he needs to be taking it back in one piece.
In the event of Pilot B overstressing the aircraft, and then he denies having touched the controls, how would Pilot A
1) Prove
2) explain
or 3) justify the course of events?
This ought to be merged with another thread running here.
http://www.pprune.org/private-flying...up-flying.html
Short answer is that if they go flying and A signed as PIC without having a valid medical then Pilot A needs to read the Colin MacRae accident report.