Whatever merits precedent may possess
The focus of this essay is to discuss the certainty in precedent. The standpoint of this essay will be in concurrence with the view of Carleton Kemp Allen that ‘certainty is the very last quality which can be attributed to merits precedent possess’.
There is certainty in the law.
On one hand, one may argue there is certainty in the law. Judicial precedent means the process whereby judges follow previously decided cases where the facts are of sufficient similarity. The doctrine of judicial precedent involves an application of the principle of stare decisis ie, to stand by the decided. This, in practice, means that inferior courts are bound to apply the legal principles set down by superior courts in earlier cases. Thus, it is regarded that the law provides consistency and predictability, and these two merits of precedent interlock with the quality of certainty. In other words, by looking at existing precedents, it is possible to forecast what a decision will be and plan accordingly. What Lord MacKay stated fully supports this view,
‘Precedent assists litigants to assess the nature and scope of legal obligations and, to the extent that it enables them to predict the likely outcome of disputes, it restricts the scope of litigation. By allowing the vast bulk of disputes to be settled in the shadow of the law, a system of precedent prevents the legal apparatus from becoming clogged by a myriad of single instances. It reflects a basic principle of the administration of justice that like cases should be treated alike and therefore generates a range of expectations from different participants in the legal process. Rules of law based on a system of precedent are therefore likely to exhibit characteristics of certainty, consistency and uniformity.’
Furthermore, the doctrine of binding precedent may help explain the certainty in the law. A binding precedent is a decided case which a court must follow. But a previous case is only binding in a later case if the legal principle involved is the same and the facts are similar. In strict practice, judges bind on precedent as they distinguish a case on its facts, or on the point of law involved. This device is used to avoid the consequences of an earlier inconvenient decision, but most importantly it is due to the fact that certainty is seen to be in the law. Such view is supported by Buckley LJ in Olympia Oil v Produce Brokers. He stated, ‘I am unable to adduce any reason to show why that decision which I am about to pronounce is right… but I am bound by authority which, of course, it is my duty to follow…  ’
Judicial precedent is based on real facts, unlike legislation. It is so detailed that it can be viewed as being practical in nature, and there is a wealth of cases to refer. In this case, one may say certainty is a merit that precedent possesses.
Certainty in the law?
However, at the other extreme, one would question whether there is any certainty in the law. The abolishment of the London Tramways rule  can be used to justify such view. The House of Lords felt that decisions of the highest appeal court should be final in the public interest so that there would be absolute certainty in the law and an end to litigation. As Lord Gardiner LC stated,
‘Their Lordships regard the use of precedent as an indispensable foundation upon which to decide what is the law and its application to individual cases. It provides at least some degree of certainty on which individuals can rely in the conduct of their affairs, as well as a basis for orderly development of legal rules.’ 
Nonetheless, the rule was criticized as being too rigid. It was also said that the rule did not produce the desired certainty in the law. The 1966 Practice Statement (Judicial Precedent) was established to replace the rule. Lord Gardiner LC further stated,
‘Their Lordships nevertheless recognise that too rigid adherence to precedent may lead to injustice in a particular case and unduly restrict the proper development of the law. They propose, therefore, to modify their present practice and while treating former decisions of this House as normally binding, to depart from a previous decision where it appears right to do so.’ 
Although the House of Lords is extremely reluctant to use the Practice Statement, as it is aware of the need for certainty and the dangers attached to departing from precedent, this does not stop to challenge the certainty in the law. In Jones v Secretary of State for Social Services, Lord Reid stated,
‘It is notorious that where an existing decision is disapproved but cannot be overruled courts tend to distinguish it on inadequate grounds. I do not think that they act wrongly in so doing, they are adopting the less bad of the only alternatives open to them. But this is bound to lead to uncertainty…’ 
One may think certainty can hardly be found in the law. For example, in C v Director of Public Prosecutions  , the House referred to the anomalies and absurdities produced by the rebuttable common law presumption that a child between the ages of 10 and 14 is incapable of committing a crime. Nevertheless, their Lordships refused to abolish the presumption, preferring instead to call upon Parliament to review it. And thus in one of the guidelines for judicial law-making Lord Lowry gave, the Practice Statement can always be used by judges in cases where precedent caused uncertainty, and as long as they can achieve finality and certainty as they change the law.
Furthermore, another view of this essay is that the changes in society over time link with certainty in the law. An example that can illustrate this is R V R (Rape: marital exemption  ), the House of Lords abolished altogether a husband’s 250 year old immunity from criminal liability for raping his wife. Their Lordships justified the decision on the basis that the case was not concerned with the creation of a new offence but with their duty to act in order to remove from the common law a fiction which had become unacceptable. In this case, uncertainty is surely raised from precedent and that Lord Keith saw the decision as an example of the ability of the common law to evolve in the light of changing social, economic and cultural developments.
Another example is Airedale NHS Trust v Bland  , the House of Lords considered the fate of a football supporter left in a coma after the Hillsborough stadium disaster. The court had to decide whether it was lawful to stop supplying the drugs and artificial feeding that were keeping the patient alive, even though it was known that doing so would mean his death soon afterwards.
Several Law Lords made it plain that they felt that cases raising “wholly new moral and social issues" should be decided by Parliament, the judges role being to “apply the principles which society, through the democratic process, adopts, not to impose their standards on society’. Nevertheless the courts had no option but to make a decision one way or the other, and they decided that the action was lawful in the circumstances, because it was in the patients’ best interests. It is difficult to follow precedent and maintain the certainty in the law.
To conclude, as the quote of Carleton Kemp Allen extends, ‘…Nobody knows, until a case has come to trial, what will emerge from all the “authorities"… Every lawyer is aware of points on which the authorities are conflicting and obscure, and as precedents multiply, so do the conflicts and obscurities’, certainty in the law should be questioned.