This is the phase in insanity that occurs when all of the symptoms of madness totally go away. The person has the capacity to objectively evaluate his actions, and he assumes legal responsibility for them. It is impossible to predict with certainty when a person would relapse into a state of insanity again because the duration of lucid interval differs from person to person and within the same person over time. Because it is extremely difficult to determine if he was experiencing mental illness at the time of the offense or was in lucid interval, he cannot be held fully accountable if he commits an offense. Intermittent lucidity is typical in melancholy and mania.
Lucid interval is also seen in cases of head injury and one can differentiate them on the basis of history , preceding symptoms , following symptoms and occurrence. In lucid interval of head injury the history of head injury and preceding symptom of concussion is present and after lucid interval there are symptoms of cerebral irritation and compression of brain and the lucid interval occurs once. In contrast in the lucid interval of insanity there is a history of insanity and the interval is preceded as well as followed by the symptoms of insanity and its occurrence is frequent.