There are visual clues as the NPC react somewhat differently laying.
The real problem with game is whole evidence collection and interpretation.
I never get what the player character has in mind and constantly end up testing what 'Lie' option says.
Dose anyone else have a problem with a slippery slope during gathering clues?
Whenever I get first few questions wrong I soon end up unable to call 'Lie' as I lack the right evidence, that effect seems to get bigger as the case progresses resulting in a poor showing.
Same. If I'm interested enough to watch then I'm going to want to play myself, and I don't want to watch someone else do it and have it spoiled.
The point isn't only to watch the game but how other people react to them and solve problems presented.
Besides that it's a perfectly good way to experience story/narrative in games without having to suffer through generic action sections.