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Judges and the law
Judges and the law

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3.4 Binding precedent

Not everything in a court case sets a precedent. The contents of a case report can be divided into two categories:

  • 1. The reason for the decision – ratio decidendi

  • The ratio decidendi of a case is not the actual decision, like ‘guilty’ or ‘the defendant is liable to pay compensation’. The precedent is set by the rule of law used by the judge or judges in deciding the legal problem raised by the facts of the case. This rule, which is an abstraction from the facts of the case, is known as the ratio decidendi of the case (see Box 4).

Box 4 Example of ratio decidendi

A couple leave their dog in their car while they pop out to a shop. For a reason that cannot later be discovered, the dog gets excited and starts jumping around. There is no issue that the dog was suffering from dehydration or being overheated. The dog paws the rear glass window. It shatters and a shard of glass flies off and, unfortunately, into the eye of a passer-by, who later has to have his eye removed. Are the couple liable to pay compensation for the man's eye? The court said no. People should take care to guard against ‘realistic possibilities’. They should only be liable, the court said, if they caused others harm by doing something that could be reasonably foreseen as likely to cause harm. We are not liable if we fail to guard against ‘fantastic possibilities’ that happen to occur. The accident in this case, the judges ruled, was just such a ‘fantastic possibility’. The couple therefore did not have to pay compensation. The reason for the decision in this case, the ratio decidendi, can therefore be expressed simply as: where harm was caused to a pedestrian by a dog smashing the window of the car that it was in, and where this sort of incident was unforeseeable, the defendants were not liable.

  • 2. Obiter dictum

  • In a case judgment, any statement of law that is not an essential part of the ratio decidendi is, strictly speaking, superfluous. Any such statement is referred to as obiter dictum. This is Latin for ‘a word said while travelling’ or ‘along the way’ (obiter dicta in the plural). Although obiter dicta statements do not form part of the binding precedent, they are persuasive authority and can be taken into consideration in later cases, if the judge in the later case considers it appropriate to do so (see Box 5).

Box 5 Example of obiter dictum

In the case above about the dog and the man injured by the shard of glass, one judge said that if you knew your dog had an excitable tendency or went mad in cars, then you would be liable if it caused someone harm in a predictable way (not in the freakish broken window scenario) and would have to pay compensation. The judge did not need to rule on that in the dog-and-the-car-window case, because the couple did not have a dog with a known excitable temperament. His observations were, therefore, made ‘by the way’ and thus can be referred to as an obiter dictum. In a future case involving a dog known by its owners to be excitable, a lawyer for an injured claimant could refer back to the judge's obiter dictum in the car window case and use it as ‘persuasive’ but not ‘binding’ authority.

The division of cases into these two distinct parts is a theoretical procedure. Unfortunately, judges do not actually separate their judgments into the two clearly defined categories and it is up to the person reading the case to determine what the ratio is. This is a bit like listening to, or reading, a speech made by a politician or a sports team manager and trying to identify what the most important part of the speech was.

In some cases this is no easy matter, and it may be made even more difficult in cases where there are three or five judges and where each of the judges delivers their own lengthy judgment so there is no clear single ratio.

In some cases it may be difficult to ascertain precisely the ratio of the case and to distinguish the ratio from the obiter dicta.

Activity 13 provides you with two illustrative examples of how to identify the ratio decidendi of court judgements. These examples highlight that this is a complex task and there is no one method of approach to determining the ratio.

Activity 13 Identifying the ratio decidendi

Timing: 0 hours 45 minutes

Please read Reading 4: ‘Ratio decidendi and obiter dictum’, which examines two law cases, Carlill v Carbolic Smoke Ball Co. Ltd and Alcock v Chief Constable of South Yorkshire Police. It outlines the facts of these cases and identifies what the ratio decidendi of each case is. This Reading is longer than previous Readings in this course, but the same advice applies as for all of them. You should read it through once to get an overall understanding of the piece. You should then read it a second time and take notes in order to clarify for yourself what is being said. You may find that you need to read through it a third or fourth time if necessary. When you have studied Reading 4, you should have a good idea of what is meant by the ratio decidendi of a case.

Now click here [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] to read the document Reading 4 (PDF, 0.2mb, 4 pages).

Having seen examples of how ratio and obiter are determined in Reading 4, Activity 14 requires you to read Reading 5 and to summarise the ratio and the obiter of the case in question. Reading 5 discusses a dispute which arose about a television advertisement for the alcoholic drink Guinness. The TV advertisement, Anticipation featured a dance routine – you may have seen the advertisement which appeared on TV from 1993 to 1994. The dispute concerned whether Guinness had copied the dance from a short film called Joy. You will be aware that it is a serious matter if students in an exam were to copy each other, or if a student was to copy another student's assignment or pass another's work off as their own. So you can see why the makers of Joy were so upset at the thought that their work had been copied. Reading 5 is shorter and more straightforward than Reading 4. You should still read the article at least twice and attempt the exercise that follows.

Activity 14 Pure genius or plagiarism?

Timing: 0 hours 25 minutes

Please read Reading 5: ‘Pure genius or plagiarism?’ and attempt the following exercise: Summarise the ratio decidendi and obiter dicta in the High Court case for breach of copyright brought by the commercial's director Mehdi Norowzian against Guinness and Arks.

Now click here to read the document Reading 5 (PDF, 0.1mb, 2 pages).

Figure 5
Figure 5: Practically every aspect of what we do can be the subject of legal disputes. When does a dance become a drama?

The GUINNESS word is a trademark. © Guinness & Co.


Mr Justice Rattee dismissed the copyright infringement action. This was the decision made in this case.

Ratio decidendi

  • He decided that although Joy was a point of reference for Anticipation, it was not a copy of it.

Obiter dicta

  • Mr Justice Rattee focused on what was being filmed and decided that such a frenetic dance was not a drama.

  • The judge stated that Joy was not a ‘dramatic work’, and therefore was outside the protection of the Copyright, Designs and Patents Act 1988.

Please note that this case was subsequently appealed to the Court of Appeal.

As has been noted previously, in delivering judgments in cases, judges do not separate and highlight the ratio decidendi from the rest of their judgment and this can lead to a lack of certainty in determining the ratio decidendi. This uncertainty is compounded by the fact that reports of decisions in cases may run to considerable length, and where there are a number of separate judgments, although the judges involved may agree on the decision of a case, they may not agree on the legal basis of the decision reached. It is for the judge deciding the case in which a precedent has been cited to determine the ratio of the authority and so work out whether he or she is bound by the earlier case or not. This factor provides later courts with a considerable degree of discretion in choosing whether to be bound by a particular authority.

The main mechanisms through which judges alter or avoid precedents are:

  • overruling

  • distinguishing.