Voluntary and Involuntary Manslaughter

Whereas the definition of murder is relatively simple, manslaughter can cover a much wider set of scenarios. In some cases, death or serious injury is intended but a partial defence exists. In other cases, there is no such intent. In some cases, an offence of murder may initially be charged, whereas in other cases it is not.  

Cases are often complex and frequently expert evidence is required. The choice of the right defence team is absolutely crucial.  

What is Manslaughter? 

Manslaughter is committed in one of three ways: 

Voluntary Manslaughter – where death was intended 

1. Where the killing takes place with the intent for murder but a partial defence applies and this reduces the offence to one of manslaughter. The three situations where this applies are loss of control, diminished responsibility or killing as part of a suicide pact. 

Involuntary Manslaughter – where death was not intended 

1. “Gross negligence manslaughter”; conduct which caused death and which was  grossly negligent given the risk of death,  
2. “Unlawful and dangerous act manslaughter”; which involved an unlawful act and a danger of harm  

Voluntary Manslaughter – partial defences to murder  

There are three situations in which an offence of murder can be reduced to manslaughter, even though the elements to prove murder are present, namely cases of: 

• diminished responsibility,  
• loss of control and  
• suicide pact. 

In each of the above situations there may well be an intention to cause death or grievous bodily harm, but the partial defence can be raised. And, whereas self-defence operates as a complete defence, these partial defences reduce guilt for murder to guilt for manslaughter.  

Diminished Responsibility 

It is for the defence to prove four elements: 

• The defendant was suffering from an ‘abnormality of mental functioning’ 
• Which had arisen from a ‘recognised medical condition’ 
• Which substantially impaired the defendant’s ability to understand the nature of their conduct or form a rational judgment or exercise self-control (or any combination of the three); and 
• It provided an explanation for their conduct 

Procedure for establishing Diminished Responsibility 

The defendant needs to show diminished responsibility on a ‘balance of probabilities’. 

Defence lawyers need to be alive to any potential medical conditions that may have impacted upon the behaviour of the defendant which may have led to the required ‘abnormality of mental functioning.’ Expert evidence will be required and this should be served upon the prosecution who will review the case.  

The prosecution will usually instruct their own expert and review the situation. 

If the prosecution takes the view that there is no longer a ‘realistic prospect of conviction’ in relation to the charge of murder, and each element for diminished responsibility is met, then a plea to an offence of manslaughter should be accepted.  

If the prosecution feels that there is still a realistic prospect of conviction, then the judge will consider whether the defence of diminished responsibility should be determined by the jury. 

Loss of Control 

This defence replaces the old defence of ‘provocation’. It is for the defence to prove three elements: 

• that there was a loss of control, which was due to a 
•  qualifying trigger, and 
• a person of defendant’s sex and age, with a ‘normal degree of tolerance and self-restraint’ and in the defendant’s circumstances, might have reacted in the same way or in a similar manner to the defendant. 

Defence lawyers should be alive to the potential for this partial defence in appropriate circumstances. Loss of control frequently arises in domestic situations. Once the defence is raised, the judge should consider whether the three elements of evidence exist. If the judge thinks the required elements exist then the onus is upon the prosecution to disprove loss of control.  

Suicide Pact 

Where a defendant kills another person as part of a suicide pact between with the deceased, then they are guilty of manslaughter and not murder. The defendant must show that there was a suicide pact, and the killing was in pursuance of the pact. 

Involuntary Manslaughter 

Where an unlawful killing takes place but without the intention to kill or to cause grievous bodily harm, the offence is manslaughter not murder.  

There are two types of involuntary manslaughter, unlawful or dangerous act manslaughter and gross negligence manslaughter. 

Unlawful Act Manslaughter 

Unlawful act manslaughter covers a wide range of situations. It may involve an assault in which there was no intent to inflict grievous bodily harm. It might involve a death that occurred during the course of a defendant fleeing a crime, for example during a car chase. It is for the prosecution to firstly prove an intentional act (as opposed to an omission); which was unlawful; and that all ‘sober and reasonable people’ would realise the act must subject the victim to a risk of harm. 

Gross Negligence Manslaughter 

The criteria for gross negligence manslaughter is as follows; 

• the breach of an existing duty of care   
• it is reasonably foreseeable that there was a serious and obvious risk of death 
•  death was caused by the breach, and,  
• having regard to that risk of death, the defendant’s conduct was so bad as to amount to a criminal act or omission 

Gross negligence manslaughter cases can involve a variety of scenarios. Many relate to medical or health care situations, as well as environments involved in childcare or care of the elderly. Other prosecutions involve deaths at work. A recent case involved the driver of a small boat crowding the channel.  

Defending these allegations inevitably involves a thorough understanding of the environment and circumstances in which death occurred. 

Olliers – specialist criminal defence lawyers 

Our senior lawyers are all leaders in their field. Olliers is ranked as a top-tier law firm by both the authoritative guides to the legal profession, namely the Legal 500 2025 and Chambers Guide 2025. We are a Times Best Law Firm 2025. We are the Manchester Legal Awards 2024 Crime Team of the Year retaining the title from 2023, an award we have won seven times since 2011.