Home owners and have-a go-heroes have for the first time been given the legal right to defend themselves against burglars and muggers free from fear of prosecution.
They will be able to use force against criminals who break into their homes or attack them in the street without worrying that "heat of the moment misjudgements could see them brought before the courts.
Under new laws police and prosecutors will have to assess a persons actions based on the persons situation "as they saw it at the time even if in hindsight it could be seen as unreasonable.
For example, homeowners would be able stab or shoot a burglar if confronted or tackle them and use force to detain them until police arrive. Muggers could be legally punched and beaten in the street or have their own weapons used against them.
However, attacking a fleeing criminal with a weapon is not permitted nor is lying in wait to ambush them.
The new laws follow a growing public campaign for people to be given the right to defend themselves and their own homes in the wake of a number of high profile cases.
In 2000, Tony Martin, the Norfolk farmer, was sent to prison for manslaughter for shooting an intruder in his home.
Earlier this year, Tony Singh, a shopkeeper, found himself facing a murder charge after he defended himself against an armed robber who tried to steal his takings. During the struggle the robber received a single fatal stab wound to the heart with his own knife.
The Crown Prosecution Service eventually decided Mr Singh should not be charged.
Until now people have had to prove in court that they acted in self defence but the changes mean police and the Crown Prosecution Service will decide on cases before this stage.
Jack Straw, the Justice Secretary, said that people would be protected legally if they defend themselves "instinctively ; they fear for their own safety or that of others; and the level of force used is not excessive or disproportionate.
He added the changes in law were designed to ensure the criminal justice system was weighted in favour of the victim.
Mr Straw and other Labour ministers have previously repeatedly blocked attempts by opposition MPs to give greater protection to householders.
In 2004 Tony Blair promised to review the existing legislation after he admitted there was "genuine public concern about the issue.
But his pledge was dropped weeks later after the then Home Secretary Charles Clarke concluded that the current law was "sound .
Two Private Members Bills on the issue were tabled by the Tories around the time of the 2005 general election, but both were sunk by the Government.
In 2004, a Tory Bill designed to give the public the right to forcibly tackle burglars was also rejected.
The new self defence law, which came into force yesterday, is contained in the Criminal Justice and Immigration Act 2008 and was announced by Mr Straw last September.
He is understood to have decided new laws were necessary after he was involved in four "have-a go incidents, which included chasing and restraining muggers near his south London home.
Opposition leaders said it offered nothing new and was merely the latest policy designed to appeal to core Tory voters.
In practice, householders are seldom prosecuted if they harm or even kill an intruder but the Act will give them greater legal protection.
Nick Herbert, the Shadow Justice Secretary, said: "This is a typical Labour con it will give no greater protection to householders confronted by burglars because its nothing more than a re-statement of the existing case law.
Mr Straw said: "The justice system must not only work on the side of people who do the right thing as good citizens, but also be seen to work on their side.
"The Government strongly supports the right of law abiding people to defend themselves, their families and their property with reasonable force. This law will help to make sure that that right is upheld and that the criminal justice system is firmly weighted in favour of the victim.
"Dealing with crime is not just the responsibility of the police, courts and prisons; its the responsibility of all of us. Communities with the lowest crime and the greatest safety are the ones with the most active citizens with a greater sense of shared values, inspired by a sense of belonging and duty to others, who are empowered by the state and are also supported by it in other words, making a reality of justice.
"These changes in the law will make clear victims of crime, and those who intervene to prevent crime, should be treated with respect by the justice system. We do not want to encourage vigilantism, but there can be no justice in a system which makes the victim the criminal."
It came as it emerged that homeowners could have to wait up to three days after reporting a crime to see a police officer, according to a leaked draft of the Policing Green Paper.
It sets out new national standards for local policing for all 43 forces cross England and Wales.
Callers to the police will be given set times within which officers will attend an incident.
The paper says that this will be
"within three hours it if requires policing intervention or three days if there is less immediate need for a police presence."
However, the Home Office would not comment on the plans.
Story from Telegraph News:
http://www.telegraph.co.uk/news/newstopics/politics/lawandorder/2303004/Have-a-go-heroes-get-legal-right-to-defend-themselves.html
