Maybe the death of an NPC should have the potential to spawn a new type of NPC somewhere off in the distance who is looking for the now dead NPC. A list of gear that the NPC died with should also be created, excluding common items like arrows, and food. And the cause of death should be recorded, as this would be important for determining the concequences of getting caught with that persons gear. The hire status of the NPC should also probably be recorded. Possible permutations could include:
-The tracking NPC spawns at a village associated with the now dead NPC and...
- stays there, waiting for the NPC to return or you would just choose a random villager already present to be the tracker instead.
- leaves the village and moves towards the spot the NPC died at.
- tracks the player directly.
The idea being that if the tracking NPC finds your character with gear that the now dead NPC was carrying/using you should have to pass a suspicion check before your Scott-free.
Moderately common items that are just of average quality shouldn't raise much suspicion (handaxes for example), but items of either high or low quality (especially masterwork). rare items (like hunting horns) should stand out more, cultural items from a culture you don't belong to should stand out more, and really value dense items like rings and bracelets should all stand out and create lots of suspicion if they where carried by the dead NPC (on the list).
The idea behind the list is that it doesn't tag the items directly as stolen, and hence give people a way to know that something is up, and it also leaves room for the possibility that the tracker who finds you may genuinely be wrong if or when they confront you.
So, when a tracker confronts you, they should compare each item they would know the deceased was carrying to the items you are carrying. Each time an item matches, there should be a roll based on the characteristics of the item for them to become suspicious of that item. If none of the items are suspicious, the NPC should still be willing to talk to you but wouldn't have much to go on. (However you wouldn't want to give that away just yet.)
The NPC should ask you if you know about the whereabouts of the deceased person, if you have seen them before, or if you hired the deceased from a village they should ask you why the deceased is not with you (and should be suspicious if they wern't already).
At this point you would have 3 options. You could tell the truth if your character knows what happened. You could make something up. Or you could simply say you don't know. If you tell the truth, and the truth is that you killed the deceased, this would be a confession. Otherwise, you would simply be telling the NPC what happened, basically listing the cause of death that was recorded by the game at the time the deceased passed on. Examples could include "{They} fell through the ice and drowned.", "{They} where {mauled/clawed/biten} by a {hostile animal or pack of animals}", "{They} froze/burned to death.", "{They} where shot by {somebody other than you}." (if that person is your companion and is still with you, they should probably freak out and make things worse), "We where attacked by {a hostile foreigner/a pack of bandits or gang of foreigners} and {They} didn't make it.", "We ate something poisonous/tainted without knowing it, and {They} died." the list could go on depending on there being new ways for an NPC to die or not. Some stories may still sound really bad though, even if they are truthful however. Especially burning to death, or dying of illness/poison.
Lying would allow you to concoct something similar to something you may say truthfully, including passing off blame onto a companion who you previously hired who is no longer with you (perhaps also dead?), and this option may curry favor with somebody if they are accidentally at fault for killing somebody (most likely by accidentally shooting somebody else), but lying would have the potential to raise suspicion if your character fails either a willpower or intelligence check.
If you say you don't know, you could either say "I've never met {Them}." or "{They} went home already, didn't they?".
At this point, the NPC would start asking about the items they think are suspicious in your inventory, and you can say stuff like "I bought {this thing}", "{this thing} is a family heirloom.", "I found {this thing}.", "I made {this thing}", or "I was bringing {this thing} back. (Stating the item belonged to the deceased.)".
Alternatively, if you are confessing to killing the deceased you would be given a chance to explain why. Reasons could include you really need something on {them} (admitting you took that item), {they} took your {thing(s)} off of your settlements, {they} killed your pet(s) or livestock (or both), {they} destroyed or where destroying your traps, {they} attacked you, {they} startled you by wandering into your cabin at night (perhaps while asleep?), is was an accident while hunting or fighting a hostile group of people, or perhaps you just don't like them. Depending on your current condition, or the time of the conflict, you may or may not garner some sympathy. For instance, you are starving and really needed their smoked badger cuts. You where freezing and really needed their overcoat. You where defending yourself (and still covered in nasty wounds).
If they version of events dosn't logically check out or is really callous, the NPC should automatically accuse you of murder and get angry. This should be triggered by obvious stuff like "I've never met them, here's their stuff.", "{they} attacked me! (and had little to no combat skill, possibly an old man, a woman, or a child)", "I really needed that masterwork bronze brooch.", "{They} stole my leaky wooden cups!"...
Anyways, if they accuse you of murder in a village, the locals should react with shock and refuse to deal with you. If you previously run afoul of the village (say by stealing things, settings on fire, killing livestock, ect), the villagers should possibly get angry enough to attack you on sight.
If they come to the conclusion that you murdered the deceased, while you both are in the wilderness, the tracker should either:
- run away back to the village (with the same precipitous drop in reputation if they reach the village).
- demand you hand back the items they think are suspicious, and then head back to the village (with the same precipitous drop in reputation if they reach the village).
- get angry and attack you directly.
If you confess and successfully elicit sympathy, they may forgive you and possibly help you with your condition (starvation, injury, or illness/poison). They may or may not still ask for the suspicious items back.
Otherwise, if they don't believe you did it or otherwise think the deceased is still alive, then you get off Scott-free.
Edit:
Since a fair chunk of murder is likely to happen in no-man's land, it might be a good idea to consider that you only think somebody is a "vagabond" because you don't know which village or culture the person actually belongs too. This would mean that attacking vagabonds in the wilderness carries more risk if you decide you want to trade their goods away. The risk is smaller overall, but it should be that much more suprising and scary if you are confronted, especially in a village. And if you earn wealth by killing people all the time, you are more and more likely to get accused of murder over time unless the tracker finds the items at the point where the deceased person died, and brings them back to the village.