对５６例精神发育迟滞患者被奸污的司法精神鉴定案例进行分析。鉴定结论，诊断为轻度精神发育迟滞１０例（１７．９％），中度和重度者各２２例（３９．３％），极重度２例（３．５％），５６例中，评定为无性自我防卫能力者５１例（９１．１％），部分性自我防卫能力者５例（８．９％）。作者对性自我防卫能力的概念及其评定提出了自己的意见，认为中度以上精神发育迟滞者可评定为无性自我防卫能力，轻度者可评定为部分或者完全性自我防卫能力。 56 cases of mental retardation were raped the spirit of judicial identification of cases were analyzed. In conclusion, 10 (17.9%) were diagnosed as mild mental retardation, 22 (39.3%) were moderate and severe, and 2 were extremely severe (3.5%). Among 56 cases, 51 cases (91.1%) were asexual self-defense ability and 5 cases (8.9%) were partial self-defense ability. The author puts forward his own opinion on the concept of sexual self-defense ability and its evaluation. He believes that people with moderate mental retardation can be assessed as asexual self-defense ability, and those with mild degree can be assessed as partial or complete self-defense ability.