Lawbringer

Lawbringer is a Fallout 3 perk.

Description
Once you have the Lawbringer perk, any evil character you kill will have a Finger on their corpse. This Finger can then be sold to a certain person (whose identity is disclosed when you take the perk) for caps and positive Karma.

The evil alternative to this is the Contract Killer perk.

This perk is required to obtain one of the Guns and Bullets books, and one of the Nuka-Cola Quantums.

Bugs

 * It is possible that Sonora Cruz vanishes from the Regulator HQ and does not return. Fast traveling to the HQ often spawns various combination of hostile creatures and/or robots. They are normally busy killing the Brahmin outside the HQ, however they engage you upon your arrival. Due to the nature of the AI and the NPC characteristics of Sonora Cruz, this causes her to flee from the area. (confirmed PC, PS3, and 360)


 * If you find the dead body of the regulator (the one containing the hit on Junders Plunkett), look closely, it is a dead body, but you may notice that it is actually blinking. Whether it needs to be a certain time or other such variables is unknown. Initially discovered during night time. (confirmed on Xbox 360)
 * Even with the lawbringer perk, regulators in the HQ will hold a bounty notice saying that you're a dangerous person who is to be shot on sight for a reward of 1000 caps. (confirmed all platforms)

Trivia

 * In Oblivion, there is a quest in which you are required to kill a man and loot a finger from his corpse, similar to the finger looted of an evil character when you have this perk. This perk may have been created to pay homage to Oblivion, since Todd Howard is the lead developer for Oblivion, as well as Fallout 3.