Due to popular demand (well, Blackrat demand), I am going to write a bit more about investigation and how it can be systematised.
Fundamentally, investigation in roleplaying is about searching for and discovering clues which can be used to draw conclusions about something happening in the fictional world of the game. If you over-mechanicise searching for clues (for example by making discovery automatic, as with Trail of Cthulhu) then you end up with something that feels like railroading. If you elide the discovery of clues and drawing of conclusions (something it’s easy for a GM worried about whether the players will be up to the task of deducing what is going on) then you end up with exposition rather than true investigation.
We can break it down further
– Following leads to direct the search for clues towards particular people, places, groups, events and so on.
– Finding the imprint left by the events one is investigating, especially if it is concealed (fingerprints, footprints, CCTV footage, a statement by a witness…)
– Identifying a pattern, an anomaly within a pattern or a definite lack of pattern (for instance, all the victims belonged to the same religion)
– Interpreting the imprints and patterns found so far to draw conclusions about what might have happened
– Making the link between an imprint, pattern or conclusion and a new lead, widening the investigation (a person whose fingerprints, footprints, etc were left at the scene; the local temple of the religious group being victimised, etc)
– Drawing a solid enough conclusion to allow a confrontation of some sort (arrest the murderer, grab the lost artifact, reunite the father with his lost daughter)
Each of these can in principle be broken down into appropriate skills or abilities (forensics, interrogation and so on), if the game system wishes, but most game systems don’t really use the above breakdown. Most systems concentrate almost exclusively on the second bullet: finding the imprint through awareness tests, while some that are more focused on investigation also move on to the third and fourth bullets, allowing skill use to draw conclusions such as “these footprints were made by a very large man”.
To me, at the heart of an investigation game is how you move through these steps, and how the elements highlighted in bold get you from one step to the next. What makes an investigation game enjoyable for me as a player (and vicariously as a GM) is taking those steps myself, not having the system do it all for me; but of course, since I am not in fact a forensics expert or arch-interrogator or whatnot, it must give me just enough information to make it possible for me to draw conclusions and decide on appropriate leads myself, rather than spoon feeding me.