请看外电相关报道：A nurse was convicted Monday and sentenced to life in prison for killing 28 of his patients at a hospital in southern Germany.

Stephan Letter was found guilty of 12 counts of murder, 15 of manslaughter and one of mercy killing in what has been described as Germany's biggest series of killings since World War II.

“安乐死”通常有两种表达，“euthanasia”和“mercy killing”，前者源于希腊语，意思是无痛苦的、幸福的死亡，常见于医学和法律文件。相比而言，“ mercy killing” 更常用于日常会话。此外，医生所采用的“assisted suicide”（辅助自杀）也属于安乐死的范畴。

自上世纪70年代以来，安乐死一直是国内外医学界、哲学界和伦理学界讨论最为热烈的问题之一，至今尚未取得一致的意见。这名“杀手天使”的律师曾在法庭辩护，该护士杀人的动机是要减少病人的痛苦。

看下面一个例句：Mr Smith indicted for the mercy killing of his incurable son. 史密斯先生被指控通过安乐死杀死他患有绝症的儿子。