The second one was a brigand lieutenant who was returned to keep and turned over to the authorities. In exchange for valuable information about the cult, the hanging sentence was reduced to life in a labor camp. The intel was very reliable and proved to be useful to the PC's.
. . .
When the party finally did encounter the leaders of the cult, there was no quarter asked or given. The cultists were all fanatical death priests and would never surrender.
Sounds very similar to my campaign world. Killing intelligent humanoid prisoners would definitely be frowned upon (though what happens in the dungeon stays in the dungeon, for the most part), so most prisoners end up with the proper authorities. Whether those authorities proceed to execute them, let them go, or keep them in a dungeon depends on the circumstances.
The most recent captures by my party:
-- Dwarven mine contractor. He'd hit silver in what was supposed to be a rock quarry, and was ripping off the mine owner (a local noble). More important, he got discovered in this by mobsters who blackmailed him into using the silver to make alchemical silver weapons for a secret organization the PC's have tangled with before. The PC's killed the secret organization people in a "kill 'em hard, kill 'em fast" assault, but captured the dwarf and turned him over to the noble. He's been in a dungeon for a few weeks, as the noble holds on to him and decides what to do. He didn't know much about the nefarious plotting, but he told them everything he knows.
-- The alchemical silver weapon making operation attracted the attention of a group of mercenaries led by werewolves. The PC's captured a werewolf half-orc sorceress in the first fight, and turned her over to the local noble. Nobody is sure if her story of being an innocent victim of lycanthropy, trapped into these life by the others, is true or not, but they are looking into curing her. She volunteered decent intel, which helped them in the next fight and likely saved many civilian lives.
-- In a later fight, they captured the werewolf/assassin/mercenary company leader, and one of his lieutenants. The PC's tried to reason with them to talk. Then the noble and his guard captain took them off screen and tried Intimidate, by unspecified means -- I just rolled the dice. I came up good, so they spilled a little more info, which was then relayed to the PC's. The prisoners are still in the dungeon of the noble's tower (in a cell not adjoining the poor dwarf!). Since they were working for an enemy country in a declared war, there's a chance they could be exchanged for friendly prisoners in the future. If the war ends without that, they'll certainly be executed, on charges of brigandage for trying to massacre a village and attempted murder for trying to kill the noble -- and also because nobody wants a werewolf assassin running free!
In my other campaign, they captured a goblin and tried to Intimidate him, using the old trick from "Untouchables" of "killing" another prisoner (who is already dead) to scare the first guy. It worked, and he answered their questions, but when he didn't know answers and they wouldn't take that for an answer, he just made things up. Eventually, after he lead around for a few hours looking for the "secret back door" to the dungeon that the goblin kept promising must actually be over there, no there -- they actually found it by accident!
Out of character, one player said, "I think the DM is just messing with us. I don't think this goblin knows anything. The DM is just showing us that torture doesn't work -- it gets an answers, any answer, but not necessarily the truth, because the guy may not even know anything, but he'd say anything to save his hide."
I had to admit "bingo" on that one and explained that I'd learned this a CIA memoir about Vietnam, and a friend who was in military intel in a war zone and later was a detective.
The PC's left the goblin prisoner tied up as they explored past the secret backdoor. Not sure what they will do in the end -- likely turn him over to the local authorities. In the past (Sunless Citadel), they made peace with some goblins, agreeing to let them leave if they'd stop fighting.