作为司法实践中最严重的犯罪之一，恶意非法剥夺他人生命的行为无论在中国、还是在美国，最高刑期都可至死刑。对杀人犯罪进行严厉的处罚不仅捍卫着个人的生命价值，也捍卫着社会的公共秩序——只有让那些违反法律规则和社会秩序的人受到应有的惩罚，才能让违法者和社会其他人意识到遵守规则和秩序的重要性。但要让惩罚有效，就必须根据违法者的罪责程度来决定刑罚的严厉程度——只有其犯罪行为受到谴责的程度是其应得的情况下才具有道德力量。因此，对杀人犯的处罚应该根据其无视他人生命价值和社会秩序的严重程度进行分配：身体伤害越严重，我们就越可以推定其具有无视他人生命价值和社会秩序的态度；罪犯伤害他人的意图越强，我们就越能指控其无视他人和社会规则。危害后果和主观恶意是区分刑罚轻重的关键因素，也是本文探讨的关键所在，即如何在故意杀人犯罪中正确对被告人进行定罪量刑。

对此，本文以美国刑法中的谋杀罪为切入点和研究对象。作为英美法系的重要代表国家之一，美国刑法关于恶意杀害他人的犯罪规定非常详细。在以出现死亡结果为犯罪构成要件的前提下，美国大部分州根据被告人的犯罪意图或恶意程度不同，将谋杀罪分为一级谋杀和二级谋杀，其中只有一级谋杀能判处死刑。在区分谋杀罪的等级时，美国刑法不仅从被告人是否经过预先的深思熟虑来判断其恶意程度，还从被告人的杀人方式、作案地点、特定的受害对象，以及造成的危害后果等方面来判断是否要予以最严厉的处罚。此外，美国的双阶层犯罪构成体系要求，在满足谋杀罪的成立要件之外，还要保证被告人不存在合法的辩护事由，否则可以减轻或免除处罚。美国《模范刑法典》甚至还列举了可以判处死刑的加重情节，以及可以从宽的减轻情节。相比于我国刑法及司法解释对故意杀人罪的规定，美国对谋杀罪的刑法规制具有鲜明的特色，对于完善我国相关立法与司法实践有一定的启示意义。

具体而言，本文共分为五章。第一章主要介绍了美国刑法中的谋杀罪相关概念、立法沿革和主要规定。美国的谋杀罪立法最早源于英国普通法，因此其谋杀罪的概念和分类在很大程度上受到普通法的影响。从概念和犯罪构成上来看，不能完全将美国的谋杀罪等同于我国的故意杀人罪，至少在犯罪意图的具体分类上，中美两国存在一定的差异。也不能简单将谋杀罪等同于“预谋杀人”。从美国的谋杀罪立法沿革来看，十六世纪英国普通法传入北美大陆后逐渐实现本土化，不仅出现了谋杀罪的分级制度，还创设了重罪谋杀规则。如今，美国的谋杀罪立法体系完善，罪责等级明确，量刑情节轻重区分明晰，并逐渐呈现出州与州之间的统一趋势。

第二章从犯罪构成体系的角度，对美国的谋杀罪各个构成要素进行了梳理。具体来说，在犯罪行为方面，作为或不作为的方式都可以构成谋杀罪，但需出于行为人自愿。在犯罪意图方面，行为人可以是概括的故意，也可以是特定的意图。在满足犯罪行为和犯罪意图的要件后，才会进入到辩护事由的判断阶段。有些辩护事由能够将谋杀罪从有罪减为无罪，包括自卫、紧急避险、被迫、未成年、精神病、错误、醉态和警察圈套等情形；还有一些辩护事由仅仅能够将谋杀罪减轻为非谋杀罪或其他处罚较轻的犯罪，例如激情杀人、不完美的自卫、胁迫等。这些辩护事由从犯罪构成的角度为谋杀罪的减轻或免除处罚提供了理论基础。

第三章从立法和司法的角度，对美国刑法中的谋杀罪各个类型及其界定展开论述。根据行为人的主观可责性，谋杀罪可分为蓄意谋杀、故意重伤谋杀、极端冷漠谋杀和重罪谋杀四种类型。其中蓄意谋杀对行为人的犯意要求为故意，故意重伤谋杀只要求行为人对重伤结果存在故意，对死亡结果有明知即可，而极端冷漠谋杀也只要求行为人对死亡结果存在明知；作为谋杀罪的特例，重罪谋杀甚至都不需要行为人对死亡结果存在轻率或疏忽。此外，从立法模式上来看，美国大部分州将前述谋杀罪分为一级谋杀和二级谋杀，并且将死刑限制在一级谋杀的范围内。

第四章以美国的谋杀罪分类在实践中遇到的困境与探索的改良为研究重点，指出美国的谋杀罪现有规制主要面临两大问题：一是谋杀罪和非谋杀罪的界限模糊不清。作为区分二者的标准，恶意预谋不仅在概念上模糊不清，还无法解释重罪谋杀的犯罪意图。二是美国的谋杀罪分级标准存在一定的不恰当性，目前所采用的预谋分级标准，除了概念模糊以外，还极容易出现行为人的主观可责性与刑罚轻重不一致的情形。对此，美国刑法也做出了相应的路径改良，通过完善对犯罪意图的界定，以及量刑情节的明确和衡量标准，来正视谋杀罪定罪量刑中可能存在的问题。

第五章在前述研究的基础上，论述美国的谋杀罪立法及司法实践对完善我国故意杀人罪的启示。首先，从犯罪构成理论来看，可以通过明确犯罪构成要素在我国故意杀人罪犯罪构成体系中的地位，以及减轻和加重的故意杀人罪，来构建定罪等级清晰的故意杀人罪框架。其次，从立法体系来看，可以通过完善从严和从宽处罚的量刑情节，来使得我国的故意杀人罪的量刑体系更具有可操作性。最后，从我国故意杀人罪与其他“致人死亡”型犯罪的关系来看，可以借鉴美国的重罪谋杀规则，将致人死亡的案件类型化，从而避免转化型杀人和结果加重犯的理论、实践之争。

As one of the most serious crimes in judicial practice, maliciously and illegally depriving human life can be sentenced to death both in China and the United States. The primary function of strict punishment for murder is not limited to defend the fundamental personal life value, but also public orders. We punish those who refuse to comply with them, and make sure there must be negative consequences for their violations, so that everyone in our society can appreciate the importance of legal rules and orders. To make the punishment effective, the severity of the punishment must be consistent with the offender's culpability degree. Only when the offender deserves it, can the punishment be properly apportioned and have moral power. Therefore, the punishment for killers should be allocated based on the severity of their disregard for life value and social orders. The more serious the physical injury is, the more cable we are to infer that the offender displays such disregard. The stronger the criminal's intention to harm others, the more we can accuse them of this ignoring. Harmful consequences and subjective malice are the key factors in determining the severity of punishment, and also the point of this Article which focus on how to correctly convict and sentence in intentional homicide crimes.

This Article starts with murder in American criminal law. Being one of the main countries of common law system, American criminal law stipulates murder in details. Under the premise that death is the elements of murder, most states in the United States classify murder into first-degree murder and second-degree murder based on the defendant's criminal intent or degree of malice, in which only first-degree murder can be sentenced to death. Murder degrees are decided not only by the defendant’s prior premeditation and deliberation, but also by the factors such as the way of killing, special occasions and victims, as well as the severity of harmful consequences. In addition, the American dual class criminal constitution system requires that, besides the elements of murder crimes, there must be no legitimate defenses, otherwise the punishment can be reduced or exempted. The Model Penal Code drafted by American Law Institute even lists aggravating circumstances that can be sentenced to death, and mitigating circumstances that can be lenient. Compared with the Chinese criminal law and judicial interpretation on intentional homicide, the regulation of murder in the United States is more systematic and logical, which has certain significance for improving our relevant legislation and judicial practice.

This Article can be divided into five chapters. Chapter 1 introduces American murder law’s related concepts, legislative evolution, and current provisions. Today’s murder law originated from early England common law, so the concept and classification of murder are largely influenced by the latter. From the perspective of concept and criminal constitution system, American murder cannot be completely equated with Chinese intentional homicide, at least in the classification of criminal intent in the two countries. Murder does not simply mean premeditated murder. From the perspective of evolution in American murder law, since introduced into the North American from the 16th century, the British common law has been gradually localized and changed, during which not only did a classification system for murder appear, but also were felony murder rules created. Nowadays, the legislative system for murder in the United States is well-established with clear degrees of criminal liability and sentencing circumstances, and gradually shows a unified trend of criminal statutes between these states.

Chapter 2 summarizes the elements of American murder from the perspective of criminal constitution system. In criminal conduct, both the act and omission can constitute murder, only if the conduct is voluntary. As for criminal intent, either general intent or specific intent is enough to satisfy murder elements. When the conduct and intent elements are satisfied, defenses will be considered to decide whether murder is committed. Some defenses can exempt defendants from punishment, which include self-defense, necessity, duress, underage, sanity, mistake, intoxication and police entrapment. There are also some imperfect defenses that can only reduce murder to manslaughter or other less severe crimes, which are not limited to killing in passion, imperfect self-defense and coercion. These defenses provide a theoretical basis for mitigating or exempting punishment of murder from the perspective of crimes constitution.

Chapter 3 discusses the various types of murder defined in American criminal law and judicial practice. According to the actor’s culpability, murder can be divided into four types, which are intentional murder, intent-to-cause-serious-injury murder, extremely indifference murder and felony murder. The intentional murder requires killing intent, while intent-to-cause-serious-injury murder only requires the actor intent to cause serious body injury and have knowledge of the death result. Similarly, extremely indifference murder only requires the actor have knowledge to create great risk in death. As a special type of murder, felony murder does not even require the actor's recklessness or negligence in the occurrence of death. In addition, from the perspective of legislative mode, most American states divide murders into first-degree murder and second-degree murder, and limit the death penalty only to first-degree murder.

Chapter 4 focuses on the difficulties and improvements in American murder law application, and points out two major defects in the existing regulations. The first one is that the distinction between murder and manslaughter is confused. As the prime difference of these two crimes, malice aforethought is not only conceptually ambiguous, but also fails to explain the required criminal intent in felony murder. The second one is the inappropriateness of the standard of murder degrees. In current murder degree system, premeditation is not the proper criteria for the severity of murder punishment, or is prone to imbalance the culpability and punishment. In response, the American criminal law community never stops in improving and reforming the old murder laws and theories. Scholars and judges try a lot in clarifying related criminal intent and sentencing circumstances, so that the existed and potential problems in the conviction and sentencing of murder can be fixed.

On the basis of above research, Chapter 5 discusses the enlightenment of American murder to Chinese intentional homicide law reform. Firstly, from the perspective of crime constitution theory, a clear framework for intentional homicide can be constructed by clarifying the elements of intentional homicide, mitigating and aggravating crime constitution. Secondly, from the perspective of the legislative system, the sentencing system for Chinese intentional homicide can be made more operational by improving the sentencing circumstances for severe and lenient punishment. Finally, from the relationship between intentional homicide and other "causing death" crimes in our country, we can learn from American felony murder rules and categorize cases that cause death into one rule, so as to avoid the theoretical and practical disputes between transformed homicide and aggravated consequential crime.