Cognitive Dissonance!
This is the feeling of uncomfortable tension which comes from holding two conflicting thoughts in the mind at the same time. Nice Grandpa could not be a killer. Or...even a grandpa can do rotten things!
Dissonance increases with:
- The importance of the subject to us.
- How strongly the dissonant thoughts conflict.
- Our inability to rationalize and explain away the conflict.
I had a grandfather that was capable of doing bad things, so the possibility of RL being involved in the homicide is NOT cognitively dissonant.