'Lucid Interval' may be seen in:

B i.e. Insanity This is a period occurring in insanity, during which all the symptoms of insanity disappear completely. The individual is able to judge his acts soundly and he becomes legally liable for his acts. If he commits an offence, he cannot be completely held responsible, because it is difficult to know whether he was suffering from some mental abnormality at the time of committing the offence. In mania and melancholia, lucid intervals are common