In The Curious Incident of the Dog in Night-time it's shown how honesty and trust is important to Chris. It is shown throughout the book as a major theme and how lies and deceit tear families apart, break down a person's mental stability and how important they are to maintain a relationship with not only family but how telling the truth is the basis of being able to love someone and by extension, the ability to relate to them.
Being able to tell the truth to the people closest to you is something Chris holds dearly, both consciously and subconsciously. There is no doubt that trust is a very fundamental part of Christopher's psyche, seen when he outrightly states that he does "not tell lies", that he simply "can't tell lies". Chris cannot comprehend lying, he defines it quite narrowly: "when you say something happened which didn't happen.", so when he starts to "think about something which didn't happen (he starts) thinking about all the other things which didn't happen." and it completely "reboots" him. This shows that lying is not something he just can't tolerate, not just something that he is simply disgusted by but it's even more basic than that. It shows that he can't handle it, so he just "shuts down", that even subconsciously he knows that it's wrong.
It's the betrayal from all the lies told to Chris that simply breaks him. That cripples him. Chris thinks that his father loves him "because loving someone is helping them when they get into trouble and looking after them, and telling them the truth". Haddon eloquently sums it up saying "Father ... always tells (him) the truth, which means that (Father) loves (him)". This is a powerful remark, it explains what a betrayal it is for Father to lie to Chris about his mother's death, it explains how excruciatingly pained he is and why he had to go to London to live with his mother and how he couldn't go back to his Father.