Colloquial Terms: The Eye, The Watcher, The Conscience, Judgment, JURY
Physical Appearance: Appears as a large eyeball that grows out of various surfaces. Only the victim is able to see it, and its gaze will always follow the victim.
Behavioral Characteristics: Usually targets people who have recently committed outlandish crimes (though it has been documented as targeting people who have only committed minor crimes as well). For a period between a week and a year, PRE17 will appear to the victim at various locations, slowly making the victim more nervous and paranoid. After some time, PRE17 will choose another victim and enter into that victim's body, merging with their consciousness. This creates a new being who identifies itself as "Judgment". Judgment will then track down and kill the original victim in a way befitting the original crime (NOTE: So if someone, say, dismembered a person, then Judgment will dismember them. Whereas if they merely lied, the Judgment might removed their tongue and make them bleed to death. Yes, these are both documented cases. --SΣ).
Shortly after conversion, Judgment's body will begin to break down. Within the span of a few weeks, the body will die.
Further Reading: This transcript of a forum conversation.