JESSE: Hey, Mr. White...hand me a drink, please?
JESSE: Yo, Mr. White...gatorade me, bitch!
I'm laughing so hard right now. You brought up a lot of good points. There are more ways that you can instigate player suspicion...one of which is pauses...but that gets kind of old fast...right?
Ways to get around that would be to include some filler words such as "Umm," but even more effective might be to have the character trip over their own words.
Mr. J: The index is in the mammoth replica.
Mr. J: The index is in the mammoth replica, no, wait, it's definitely in the dungeon.
Where the fuck is it? Is Mr. J just a fuckwit or is he trying to lure you into the dungeon because a cybernetic cyclops ogre will assimilate you into its nervous system if you venture into its depths. Who knows?
Also a character tripping over their own words can show they are holding something back as well and indicate they are nervous.
Mr. J: Megan's children's book is, ha, I mean the index is in the mammoth replica. Sorry, I must be tired...
What! Megan has been missing since the beginning of the game. Wtf? Is Mr. J tired because he has been torturing Megan the entire time?
Anyway, this is fun.