Voadam said:Did the paladin think the cleric was supernaturally causing the problems and afflicting his comrades? If so not evil, no violation of code, it is his job to smack down evil active threats.
Did the paladin cut down the cleric "because she's evil" and he didn't want the distractions while dealing with the comrades' mess. If so then gross violation of the code's act with honor requirement and loss of paladin powers.
Did the paladin cut her down because she smiled and it pissed him off? Evil act, loss of paladin powers.
Good points. I should have added that if the paladin had accepted the priest's surrender then he's obligated to treat him honorably unless he can be shown as a real threat. Consider that the "lawful" part of "lawful good". A quick-thinking DM could ask why he did that. If the answer was that the paladin suspected that the cleric either was causing or could effect the situation then no loss of paladinhood. If it's that he couldn't trust the prisoner to stay put while he put out the fire then he should immediately become an ex-paladin.