Now, when we speak of voluntary manslaughter, in fact the defendant has been charged with murder but he pleads manslaughter because there is a mitigating factor such as provocation or diminished responsibility which will permit a jury to bring in the lesser verdict of manslaughter. This is important because with murder a life sentence is mandatory, whilst a conviction for manslaughter permits a judge to impose any sentence he likes - from life imprisonment to an absolute discharge.
On the other hand, involuntary manslaughter is a type of manslaughter with which a defendant may be charged. In other words, it is a crime in its own right; and please take note: throughout this and the next lecture, when I speak of manslaughter, I am referring to involuntary manslaughter. OK, so let's go! There is good news and bad news. The good news is that we can skip over the actus reus of manslaughter because it is the same as for murder.
So, the way in which manslaughter differs from murder (and voluntary manslaughter) is in its mens rea. The bad news is that the mens rea aspect is a bit of a monkey. Anyway, the easy bit first: defined in very general terms, the mens rea of manslaughter is anything other than intention to kill or intention to cause grievous bodily harm. In other words, the mens rea for manslaughter is anything other than the mens rea for murder.
It is, therefore, possible to identify four states of mind that might give rise to manslaughter: realising a risk and deliberately running that risk - subjective CUNNINGHAM recklessness; failing to consider a risk when a reasonable person would realise that risk - objective CALDWELL recklessness; and a mistaken belief that there is no risk when the reasonable person would realise there is a risk - negligence; and lastly intending to do an unlawful act which the reasonable person would realise is likely to cause immediate bodily harm, however slight.
This last state of mind - intending to do an unlawful act et cetera - is the mens rea of what is termed constructive or unlawful act manslaughter. The other states of mind we will deal with in the next lecture. Now, there are two elements to constructive manslaughter: the defendant must intend to do an act which is unlawful and the act must be dangerous to the extent that a reasonable person would realise that it was likely to cause bodily harm, however slight.
You may be able to imagine these types of cases in your own mind: people throwing things off bridges onto motor cars; assaults less than section 18 OAPA; but not usually road traffic offences which have their own specific offences under the Road Traffic Act 1988. It is clear, therefore, from the first element that the defendant must commit a crime; an act is only unlawful for the purposes of constructive manslaughter if it is a crime.
So, for example, if death results from a civil matter, then we are not talking constructive manslaughter. As Field J said in R v FRANKLIN (1883) 15 Cox CC 163, where a civil trespass had caused a fatality, 'The mere fact of a civil wrong committed by one person against another ought not to be used as an incident which is a necessary step in a criminal case. ' Again, a mistake may not be a crime. In R v LAMB  2 QB 981 - CA, the defendant pointed a loaded gun at the victim, his friend, in jest.
He did not intend to injure or alarm the victim and the victim was not alarmed. Because they did not understand how a revolver works, both thought there was no danger in pulling the trigger; but, when the defendant did so, he shot the victim dead. The defendant was not guilty of a criminal assault or battery because he did not foresee that the victim would be alarmed or injured. As Sachs LJ said, 'It was not unlawful in the criminal sense of the word. '
However, whilst Lamb was not guilty of constructive manslaughter because the unlawful act was incomplete, he might have been found guilty of manslaughter on the basis of gross negligence which I shall deal with soon. In the meanwhile, we will turn our attention to the second requirement of constructive manslaughter - that the act must be dangerous to the extent that a reasonable person would realise that it was likely to cause bodily harm, however slight.