This study is a contemplation on the testimony of the children with developmental disability during trial related to the sexual violence against them. This study examined the effect of the testimony of the children with developmental disability on the precedents from the viewpoint of the key issues pertaining to the disability welfare. Contents of the precedents were analyzed mainly from the ‘victims’ perspective’ and ‘aggressors’ aspect’ when it comes to the testimony of the children with developmental disability. This study’s analysis demonstrates that there is a need for indices for the judgement of probative force during trials pertaining to the testimony of the children with developmental disability since there are precedents in which aggressors were declared innocent since probative force of the evidence presentation ability was denied in relation to the testimony of the children with developmental disability. This study presented alternative measures for the testimony of the children with developmental disability during trial since trials fail to examine the characteristics of the children with developmental disability properly. Moreover, this study mentioned the need for re-examination of the sentence from the aspect of the welfare of the children with developmental disability in relation to the aggressors’ punishment and to the protection of the human rights of the victims who are the children with developmental disability. However, this study may be limited in the sense that it examined precedents centered on the publicly accessible precedents.