The case of Tony Martin, in 2000, has caused a great deal of heated debate about burglars, and what the law allows if you confront one in your own home. What follows describes the law, and does not stray too far into questions about what the law should be. Nor do I wish to express an opinion directly on the Martin case. Mr Martin confronted two burglars in his own house, he shot at them, and one later died. He was convicted of murder. What should he have done?

Two wrongs do not make a right. It is a grievous crime to enter another's house to steal, but it remains a crime also to assault another. The law makes no direct connection which might allow you to punish the intruder yourself. If you do take action, there are two ways in which your action might be defended. You have a right to make a citizen's arrest, and, second, you may suggest that your action was in self defence. Leaving aside the idea of citizen's arrest (very risky), we will discuss the second. The law refuses to lay down strict rules about what degree of violence can be used to defend oneself. It applies fairly simple tests, with certain additional parameters to assist.

To show self-defence you must:

1. show that you reasonably fear immediate attack.
2. show that you had no alternative avenue of escaping the attack. If you can, you must run away.
3. your response must be proportionate to the threat. If someone threatens you with a balloon, you may not respond with a knife. If your own life is not under threat you cannot threaten somebody else's life.

The situations in which assault takes place vary infinitely. No one situation is the same as the next. Every clarification which helps to fix this line more securely, will lead to manipulation on one side, and to excess violence on the other.

These questions relate to a judgement you make. That judgement occurs in your own head, and nobody else can really know what happens in someone else's head. A genuine but unreasonable or factually incorrect belief is sufficient. Where your belief is clearly out of line with the facts, this is reflected in a greater reluctance to accept that the belief is genuine.

Moreover, and above all, that belief is formed (usually) in a moment. The judgement you make must be reached, and acted upon within a very few and bewildering seconds. Courts do allow that a decision made in this way, must not be judged as if reached after sober meditation.

Another very important protection is that once a defendant has shown enough to raise the defence properly as an issue, the prosecution is then obliged to prove that it was not self-defence. The person accused is given this very significant 'benefit of the doubt'

The case should not mislead. The defence of self-defence remains very much alive and (in an eminently reasonable way only of course) kicking. It should not be assumed from the Martin case that one cannot defend oneself against a burglar. Martin got it badly wrong and paid the price. Many others who defend themselves properly are not prosecuted and are never heard of.

What the case does reveal is how, in practice, many people have a very exaggerated fear of how burglars operate. There are cases where burglars are violent; my own family has suffered. It must be remembered however, that though burglary is fairly common, most burglars go a long way out of their way to make sure that a house is empty, and violence by burglars is remains quite rare.

We cannot give safe, or universal advice. Each house, each house-holder, and indeed each burglar and each burglary is different. If you are at home, and hear the sounds of an intruder downstairs, the likely right thing to do is to ring the police (if the phone is by the bed), and then to make some noise which is likely to be heard by the intruder, but which does not necessarily mean, to the burglar, that you have heard him. Examples might be flushing the loo, or dropping some heavy object on the floor. The idea is to make it clear that the house is occupied. The high probability is that the intruder will have entered the house believing it to be unoccupied. If alerted that he is wrong, he will take the opportunity to get out without a confrontation.

However weak this sounds, do not seek to protect your property in this situation. Insured or not, you are better avoiding a confrontation, and the precise reverse of what you want is to corner the intruder.

The world of police detection is changing. It is almost impossible for a burglar to enter and leave your house without leaving some personal trace. In the past a fingerprint was required, nowadays a tiny blood sample (from a broken glass), or a hair, is enough to provide a DNA sample. As each year goes by, a greater and greater proportion of the criminal population is finding its way onto the DNA database. No promises, but if a sample is found, and recorded, when your burglar is next arrested (as he will be), and his DNA is checked, he will face an accusation with regard to your burglary.

A note to confirm that, on appeal, Mr Martin persuaded the judges that he was not entirely responsible for his actions, and a verdict of manslaughter was substituted. He will serve a further period in jail, but not a huge time, and in any event rather less than before. I think the judges have it about right.