Today most countries divide wrongful killings into the two broad categories of murder and manslaughter. The latter applies when the offender is less culpable: that usually turns on his or her state of mind (known in the legal world by the Latin term mens rea) or the circumstances. Specific definitions differ from country to country. In America first-degree murder involves premeditated killing, such as lying in wait for someone with a gun. (Prosecutors say that Mr Lloyd was murdered in an "execution style" shooting.) Second-degree murder usually involves killing on the spur of the moment, or where the offender intends to inflict serious harm but realises it may cause death. Similarly, under the law of England and Wales, a killing is regarded as murder not just when the offender intends to kill, but also when they mean to cause grievous bodily harm and actually cause death. By contrast, a killing is considered to be manslaughter in cases where the defendant did not mean to kill but was grossly negligent—for example, if a doctor fails to notice that a ventilator tube has been disconnected—or caused someone's death while carrying out an illegal act. In England and Wales, manslaughter can also result from a murder charge when a partial defence is proven: this can include a mental condition that diminishes responsibility for the crime, or where there has been a “loss of control”. (When a full defence such as self-defence is proven, the defendant is not guilty.) - www.economist.com