The Prevalence and Psycho-Social Risk Factors of Indiscriminate Murder: No Man Is an Island?

無差別殺人的盛行率與心理社會風險因子：獨活孤島之人？

本文目的是釐清所謂「無差別殺人」（或一般稱「隨機殺人」）的定義，透過實證資料分析此類殺人犯在臺灣之盛行率，及其心理及社會風險因子。研究設計問卷，通過學術倫理審查後，在全國各監獄選出符合條件之殺人犯（含無差別殺人犯）測驗，共獲得有效樣本209人，問卷成功率為91%。另一組對照組則以網路廣告取得無前科社區成年人，樣本共100人，有效數為98人。經分析，發現殺人犯中，符合無差別殺人定義之受刑人占5%，陌生殺人者占28%，家內殺人占30%，熟識者殺人占37%。我國無差別殺人之盛行率粗估為每十萬人口中0.04。本文也發現與對照組比較後，無差別殺人組之心理與社會風險因子，除同理心顯著較低、缺乏親密關係、較高的學業中輟率外，不論是自尊、暴力態度、憤世嫉俗心態、憤怒感、社會疏離感、社交焦慮、精神疾病、反社會傾向、孤獨感、憂鬱傾向、物質濫用、前科、高風險家庭等因子均與常人無異。簡言之，本研究證據顯示無差別殺人其與常人或其他殺人組更多的區別是其社會關係缺陷或缺乏社會羈絆問題（如缺乏親密關係、過早脫離學校、反社會傾向、孤獨感或社會疏離感）。這群人的社會心理特徵中，明顯缺乏建立社會關係之能力，長期孤獨並背向社會生活。從另一個角度觀察，或許是社會遺忘了這群人太久，使得他們成為社會隱形人，終了選擇以無差別殺人方法再度與社會連結。

The aims of this study are to clarify the definitional issues pertaining to indiscriminate murder and to analyze prevalence and risk factors of such crime. A specially designed questionnaire was distributed to a control group (n=98) who were over age 20 without any court conviction and recruited from internet advertisement and four offender groups (n=209) from nationwide prisons. The valid response rate was 91% for the offender group and 98% for the control group. The offender group was comprised of indiscriminate (5%), stranger (28%), domestic (30%) and acquaintance (37%) murderers. We estimated that the prevalence rate of indiscriminate murder is about 0.04 per100,000 residents in Taiwan. Other findings are, first, compared with the control group, indiscriminate murderers had much lower empathy, failed to form intimate relationships and with high school dropout rates, there were no significant differences among the five groups on self-esteem, violent attitudes, cynicism, high risk family, psychiatry illness history, anger, depression, substance abuse, unemployment, juvenile/adult prior convictions. Second, among the four murderer subgroups there are no statistically significant differences in the rates of psychological factors such as self-esteem, violent attitudes, cynicism, high risk family factor and psychiatric illness history. However, the indiscriminate murder subgroup has significantly higher antisocial tendency than domestic murder subgroup, and higher loneliness and social alienation than stranger murder subgroup. Our analysis suggests that there is no significant association between indiscriminate murder and mental illness, substance use and prior conviction. The indiscriminate murder subgroup lacked capabilities to build up proper intimate, school and social relationships, and have been isolated psychologically and somehow turned their backs on the world. Nonetheless, to argue it the other way around, perhaps the situation is created by society’s making them socially invisible by leaving them out of social connections.