We studied a stability of a twisted nematic liquid crystal with a photosens
itive chiral dopant under homeotropic boundary conditions. Transition betwe
en the homeotropic and twisted alignment induced by photochanges in twistin
g agent and anchoring strength show hysteresis. The period of the "fingerpr
ints" texture of twisted nematic changes discontinuously under the continuo
us changes of the concentration of twisting agent.