In the context of domestic abuse, much denial is deliberate lying. The legal system can re-inforce this by treating what cannot be proven as something that did not happen.
But also, there are situations in which memory is laid down differently and less clearly. Intoxication, dissociative rage, and deep shame are three that are very common in domestic abuse. However, it is not legitimate to conclude that a person is not responsible for what they do not remember clearly. It is at these times that other sources of recall are important, such as spouse reports, police reports etc. Refusal to use these to fill in gaps because they differ from one's self image is also denial.