August 2015.
Real scumslips are extremely rare, and as others have mentioned involve a scum exposing specific knowledge they shouldn't have, that goes beyond something that a town player could reasonably be guessing at, and also not be information that a player could possibly have gained from a real town role. In Steven Universe mafia, one of my scumbuddies slipped info about the role of another member of our scumteam, that she thought had already gone public, but hadn't. This was caught and led to their back to back lynches, splitting the game wide open.
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I see accusations of scumslips thrown around all to frequently and they are basically always wrong, and most of the time the accused is town (as statistics would dictate if there is no solid basis behind it). A scumslip should only be considered after careful research to exclude all other reasonable possibilities has occurred.