This article examines a Supreme Court decision on November 11, 2010(docket number 2010Do7955). The rule of prohibition on disadvantageous alteration(the rule against the disadvantageous alteration) in Korean criminal procedure code prescribes not to sentence more serious punishment than the punishment sentenced by judgement of the original instance in case of defendant appeal case and appeal case for the criminal defendant.In this case, the originally sentenced punishment was the “imprisonment of upper term 7 years, lower term 5 years” in addition to imposing the sanction of 5-year electronic monitoring(electronic tagging), and the court of appeal imposed the sanction of 20-year electronic monitoring while it reduced the length of imprisonment to “upper term 5 years, lower term 3 years”.This Supreme Court decision indicate that the nature of the court order imposing electronic monitoring is a kind of probation, and Supreme Court decided that court of appeal did not break the rule of prohibition on disadvantageous alteration in light of the nature of the electronic monitoring.In this article, I review the monitoring system for sexual criminals, along with overseeing “The Act on attachment of electronic device for position tracking on specific crime offenders”, and then I analyze the Supreme Court decision regarding the rule against the disadvantageous alteration in Korean criminal procedure code. In this article, I argue that it might comprise the disadvantageous alteration if the length of probation(electronic monitoring) was altered essentially too much. Lastly, I examine the Supplementary Provision of “the Act on attachment of electronic device for position tracking on specific crime offenders”, which apply the act to the criminals who committed crimes before the act was amended, is against “The Prohibition of ex post facto law”.

This study has considered on basis of constitutionality that the attachment order of electronic device for tracking location doesn't violate the principle of prohibition against double jeopardy, over-prohibition, and rights to equality. The attachment order of electronic device for tracking location doesn't violate the principle of prohibition against double jeopardy because it is a security measure to restrict freedom without imprisonment. However double assessment of second conviction dangerousness at additional punishment to repeated offense and sentence of the attachment order of electronic device for tracking location could be raised objection of double jeopardy. A sex offence has a character that second conviction dangerousness and crime victimization are serious. Thus to release sex offenders is very dangerous, and protection of victims and social defence are necessary. Therefore the attachment order of electronic device for tracking location doesn't violate the principle of over-prohibition because there is a balance between human rights violation and public interest. The attachment order of electronic device for tracking location is applied special offences, but it doesn't violate the principle of rights to equality because of a sanction to character of sex offenders.