What I warn you to remember is that I am a detective. Our relationship with the truth is fundamental but cracked, refracting confusingly like fragmented glass. (1.1)
How "cracked" does the truth have to be before it becomes an outright lie?
"Everything about undercover bothered me," Cassie said. "Everything." (1.68)
While she doesn't elaborate, we imagine the whole lying thing didn't sit well with Cassie. She's usually very candid and honest.
I knew, of course, that I should tell O'Kelly, now that I was working on a case that looked like it might be connected to that one, but to be frank I never for a second considered doing it. (3.3)
A lie of omission never hurt anyone, right? Should Rob have come out and told O'Kelly early on? Why did he want to be on this case so badly?
"I saw this guy come down the road and go into the estate." (3.75)
Mel suspects Damian is lying. No one else saw this man…
When I first went to boarding school I told my dormmates I had a twin brother. (3.198)
Seems like Rob has been lying for a long time. Why does Rob lie? Is it to gain sympathy from other people? To make himself feel better? Honestly: We're asking.
Sam has tendency to directness that I've always found slightly startling, in a detective. (5.45)
As a liar, Rob seems to be surprised that other people don't actually live their lives in a haze of deceit.
I didn't believe [Rosalind]. The lie was transparent—something that size, someone would have mentioned it during the door-to-door—and it went straight to my heart […] because I recognized it. (9.250)
Rob believes Rosalind is lying when she says that an orchestra performed one of her sonatas. She is lying, and this is one of the only times Rob notices, because he, too, is the type of person to overinflate his accomplishments. He did it with Cassie when they first met.
"Yeah," [Sam] said after a moment. "It was." His breathing was fast and shallow. (18.38)
Sam almost goes into shock when he finds out that his uncle isn't the honest man he thought he was. Yes, it's a little naïve of Sam to think his politician uncle is honest, but for someone as earnest as Sam, this discovery shakes his belief system.
"No conscience, no empathy, pathological liar, manipulative, charming, intuitive, attention-seeking, easily bored, narcissistic, turns very nasty when she's thwarted in any way…" (23.183)
Cassie is describing Rosalind here, but she might as well be describing Rob, although he isn't as nefarious as Rosalind is. After all, he rarely empathizes with others, he tells us he's a liar, he's charming, he wants attention, he always talks about himself, and as soon as he sleeps with Cassie, he turns very nasty.
I think [Cassie] transferred because she had lied to O'Kelly and she had lied to Rosalind Devlin, and both of them had believed her; and because, when she told me the truth, I had called her a liar. (25.66)
Cassie is one of the few honest characters in the book, but the situation drives her to lie to people… and it turns out she's really good at it. She's much better at lying than Rob, and that guy lies for a living and a hobby.