[fouc]

The ethics behind this is has been deeply studied and debated, and the "right to representation" is an important right. The system is based on checks and balances, and there's no certainty the violent criminal is guilty for the specific crime they're being charged with.

This is likely related to the adversarial nature of the courts, prosecutors vs defenders. Defenders ethically need to defend equally, basic game theory, aka Prisoner's Dilemma.