Dead players should refrain from trying to influence the game in any way. This includes trading information about the game with live players, acting as accomplices, pointing assassins or targets out to players or otherwise intentionally doing anything likely to influence the course of game events. In particular, the dead must not discuss the incident in which they died with anyone. Players may not get dead players to open doors for them or check their mail in the same way that they may not get non-players to do so.
If you have been killed, you should not announce this to anyone until you are sure that the information could not be used to track down your killer; preferably, you should wait until the report of your death is on the website. This particularly applies to those using the #assassins IRC channel.
Dead players may, of course, rejoin the game as police.