Committing crimes using technology is on the rise nowadays and one of them concerns insult or defamation through electronic media. Rude or gross words can be categorized as insult or defamation if the victim feels insulted and unhappy with the words which said to him/ her, thus may be liable according to the provisions contained in the Indonesian Criminal Code. Bad mouthing can be done directly or indirectly through social media, SMS, telephone, or other media and if transmitted through a SMS or telephone, then it may be imposed as stated in Law No. 11 Year 2008 about Electronic Information and Transaction. Therefore, if charged with this Law, an explanation is required to understand the relative competence by using locus delicti theory of a crime and there is also need to know the right method to prove a case with characteristics like these. As seen in the cases of Decision No. 232/Pid.B/2010/PN. Kdl and Decision No. 45/Pid.Sus/2013/PN. Pt whereby the defendants in those cases insulted or defamed the victims. But unfortunately, those decisions did not explain the concept of locus delicti of the crimes committed and after going through a long process of analysis, it is explained that the locus delicti theory from that kind of crime is the result theory. In the analysis section is also discussed about the proof of cases based on evidence and elements of the act against the law, therefore itu can be concluded that in the cases using an electronic media, required three types of experts which are telematics expert, languange expert, and a criminal law expert. It is also found that these cases can be categorized as crimes that are contravene to formal law. The research utilized the normative research method using secondary data by analyzing the cases and also linking these cases with applicable laws.