The judgment of the court below is reversed.

The sentence of sentence against the defendant shall be suspended.

1. Although the defendant's act of assaulting the victim does not constitute a legitimate act under Article 20 of the Criminal Act, the court below erred in the misapprehension of legal principles as to legitimate act, which affected the conclusion of the judgment, on the ground that the defendant's act of assaulting the victim does not violate social rules, as an act of passive passive defense to protect the mother of the defendant from an unfair behavior by the victim.

2. An ex officio determination prosecutor applied for the amendment of a bill of amendment to the indictment in the facts charged in the instant case, which read “to attract the victim’s arms and clothes to the degree of tearing” among the facts charged. The judgment of the court below became impossible to maintain as is any change in the subject of the judgment and the subject of the judgment of the court below.

However, despite the above reasons for ex officio destruction, the prosecutor's assertion of legal principles is still subject to the judgment of this court, and this is examined.

3. Judgment on the misapprehension of the legal principle by the prosecutor

A. The "act that does not violate the social rules" under Article 20 of the Criminal Act refers to the act that is acceptable in light of the overall spirit of legal order or the social ethics or social norms surrounding it. Whether certain act is legitimate that does not violate the social rules and thus, the illegality should be avoided, based on specific circumstances, and it should be determined individually. Thus, in order to recognize such legitimate act, the following requirements should be met: (i) legitimacy of the motive or purpose of the act; (ii) reasonableness of the means or method of the act; (iii) balance between the protected interests and the infringed interests; (iv) urgency; and (v) supplementaryness that there is no other means or method other than the act.

B. (See Supreme Court Decision 2003Do3000 delivered on September 26, 2003, etc.).