A two-tier structure for the crime of murder would not be accepted by the public and could blur the lines between accidental and intentional killings, MPs have heard.

The House of Commons’ justice committee today discussed proposals by the Law Commission to introduce new categories for murder – first-degree, where a murder is intentional, and second-degree, where murderers do not intend to kill.

Life imprisonment would not be mandatory in second-degree cases.

The proposed shake-up has been on the cards since 2005 when the commission proposed changes to homicide laws.

During today's session, justice minister Oliver Heald said the introduction of the new system would mean downgrading some instances of murder to a second-degree category, which the public would not accept.

David Ormerod QC, law commissioner for criminal law and professor of criminal justice at Queen Mary University, also said there were difficulties in extending the second-degree murder label.

‘If there is a lower threshold of culpability would the public be content adopting the sentencing regime [for second-degree murder] in relation to what we have for manslaughter?' he asked. 

‘In some cases people are released after five years. What would the reaction be if someone is released after two and a half years? [assuming they serve half their sentence],’ he said.

Paul Bogan QC, a barrister at 23 Essex Street and a member of the Criminal Bar Association, said sentencing in some manslaughter cases could sometimes stretch to 12 years.

Giving an example of a fight outside a pub, he said that if there was a spontaneous ‘one punch or push’ where the instigator intends no worse than a bruise it would be ‘difficult to say they should be convicted of murder’ under the second-degree category.

‘If the assailant’s intention was to bruise someone and that is all that happened then the guilty party would probably only get a fine and at worst a community sentence,’ Bogan said.

He added: ‘The fact that the victim may have tripped, fell over backwards, cracked their skull and died is the difference between a homicide offence and a magistrates' court trial ending in a fine. It’s difficult to see why the distinction should be so great between perhaps a £100 fine and life in jail by virtue of an accident.’

Heald added that prosecutors should continue to use the controversial ‘joint enterprise’ laws, which allow an accomplice to be treated in the same way as the person who committed a murder.

In February, the UK Supreme Court ruled that the principle had been wrongly interpreted for 30 years.

Asked by MP Rupa Huq if there were cases where joint enterprise should have been applied but wasn’t, Bogan said although victims may like to see large numbers convicted the ‘reality is they may well be disappointed’.