Andy McSmith: What that word 'reasonable' actually means

It is not often that a generalisation by a politician is followed so quickly by a serious example in real life. It was only on Tuesday that David Cameron told journalists at a press conference in 10 Downing Street that the government was going to clarify the law to ensure that people who use 'reasonable force' to protect their homes from intruders.

Two days later, four masked men who broke into a house in Salford. There was a fracas, and one of the burglars received a stab wound which proved fatal.

The fact that the householder, Peter Flanigan, his son Neil, and Neil's girlfriend were arrested yesterday does not automatically mean they will be charged with murder or any other offence. First, it will be for the police and prosecution service to find out exactly what happened.

Cases like this are very rare, and it is a strange coincidence that this one should happen so soon after David Cameron said words that may give heart to the Flanigan family: "We will put beyond doubt that homeowners and small shopkeepers who use reasonable force to defend themselves or their properties will not be prosecuted."

Mr Cameron's remarks appear to promise much, but could mean very little in practice. The law already says that a person can use 'reasonable' force in self defence. The rub is what that word 'reasonable' actually means.

That does not include killing a burglar who is presenting no physical threat. The Norfolk farmer, Tony Martin, was convicted of murder in 1999 after he disturbed two burglars in his isolated home and opened fire as they ran away, hitting one in the back. The conviction was reduced on appeal to manslaughter on the grounds of diminished responsibility.

In December 2009, two brothers from High Wycombe, Munir and Salem Hussain, were convicted of grievous bodily harm after they had chased a burglar down the street and beat him with a cricket bat, causing permanent brain damage. The burglar was part of a gang who broke into the Hussain home wearing balaclavas and tied them up.

Both cases generated huge controversy because they involved law abiding householders being jailed for offences committed against criminals under extreme provocation. It was part of last coalition agreement that they would examine this aspect of the law, yet no government could legislate to allow armed householders to administer their idea of instant justice by keeling or injuring burglars who are trying to get away.