CoveZombie wrote:

visiting Talos IV is the only death penalty
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Well, let's see.
Visiting Talo Four could be the only death penalty within Starfleet's justice system, while in Federation member's civilian courts the death penalty is the preferred consequence for murder/homicide. Especially if you're killing people by the hundreds.
M5 is debatable a self aware sapient being, but it isn't a Starfleet officer or crewman. M5 is a "civilian."