In the eyes of the law, insanity exists when there is a complete deprivation of intelligence in committing the act. Mere abnormality of the mental faculties will not exclude imputability.
The basic principle in our criminal law is that a person is criminally liable for a felony committed by him. 37 Under the classical theory on which our penal code is mainly based, the basis of criminal liability is human free Will. 38 Man is essentially a moral creature with an absolutely free will to choose between good and evil. 39 When he commits a felonious or criminal act ( delito doloso ), the act is presumed to have been done voluntarily, 40 i . e ., with freedom, intelligence and intent. 41 Man, therefore, should be adjudged or held accountable for wrongful acts so long as free will appears unimpaired. 42 In the absence of evidence to the contrary, the law presumes that every person is of sound mind 43 and that all acts are voluntary. 44 The moral and legal presumption under our law is that freedom and intelligence constitute the normal condition of a person. 45 This presumption, however, may be overthrown by other factors; and one of these is insanity which exemp...