Snap
From the final report on Perpignan (p97):
The triggering of the first stall warning in normal law, at an angle of attack close to the theoretical angle of attack triggering the warning in landing configuration, indicates that angle of attack sensor 3 was working at that moment.
Specifically:
At 15 h 45 min 05, the aeroplane was at 2,910 ft altitude and a speed of 99 kt. Pitch angle was 18.6 degrees. The stall warning sounded.
At 15 h 45 min 15, the flight control laws, which were in normal law, passed to direct law.
i.e. the Stall Warning started in Normal Law, ~10s prior to the change to Direct law...