Ratio Decidendi

The meaning of ratio decidendi is Latin for “the reason,” or “the foundation for” a decision. For example, ratio decidendi in the field of law refers to the moment or principle in a case that ultimately determines its outcome. Ratio decidendi is a legal rule regarding the legal reasoning behind the judgment of the judge or jury. To explore this concept, consider the following ratio decidendi definition.

Definition of Ratio Decidendi


rāSHēō  desəˈdendē


  1. A Latin term referring to the reason for a court or jury coming to a particular legal decision.



What is Ratio Decidendi?

Ratio decidendi is a legal phrase that translates from Latin to mean “the reason,” or the motivation behind a legal decision. Ratio includes all of the principles a court relies on – be they moral, political, or social – to justify their reasoning for coming to a decision in a case. A ratio is comprised of the legal points made by all the parties to a case. All of the other statements in the case make up the obiter dicta, which are not legal arguments on which a case can stand.

Difference Between Ratio Decidendi and Obiter Dicta

The main difference between ratio and obiter dicta is the information under scrutiny. For example, ratio decidendi refers to the facts of the case, those things that no one can debate. Obiter dicta, on the other hand, is everything in between. Obiter dicta translates to “by the way,” and refers to information that a person says, “in passing.”

In other words, difference between ratio and obiter dicta lies in the fact that, while ratio is binding in its facts, obiter dicta refer to persuasive statements only. For instance, obiter dicta may include the statements a lawyer tells the jury in a criminal case to convince them of his client’s innocence, in addition to the facts of the case.

Binding and Non-Binding Precedent

Every decision that an appellate court makes affects the decisions that all trial courts will make in the future. The name for this process is “setting precedent,” and it essentially sets up the rules for all future courts to follow when deciding cases of a similar nature. They can then refer back to prior decisions made by the higher courts to guide them on how best to rule in the case before them.

Having said that, there is such a thing as “binding” and “non-binding” precedent. What this means is that some decisions are binding, and that the lower courts must follow those decisions made by a higher court when deciding a case that has similar elements. Non-binding precedent, on the other hand, refers to a decision made by an equivalent court. In other words, one circuit court can review another circuit court’s decision for guidance, but that court is not bound to follow the decision the other court made because they are on equal ground.

Where ratio plays into both of these situations is that it helps form the basis for the decisions in either case. Therefore, in cases where binding precedent exists, courts would do well to pay particular attention to the ratio in these cases. Ratio decidendi in cases establishing non-binding precedent may be important as well, but equivalent courts may not have to observe them as closely.

Finding Examples of Ratio Decidendi

Finding ratio decidendi examples in a case is one of the hardest things a lawyer can face when referring to precedent while writing a legal brief. Some ways in which lawyers can better establish ratio decidendi examples in a case include:

  • Reading the Entire Case – Skimming a Court decision isn’t always going to cut it when trying to find the rationale behind it.
  • Reading the Headnote – Sometimes all the ratio decidendi examples a lawyer needs – or at least most of them – he can find by simply reading the headnote.
  • Finding the Epiphany Moment – While reading the case summary, a lawyer can pinpoint the rationale if he finds those key moments that ultimately convince the court of the defendant’s guilt or innocence.

Ratio Decidendi Example Involving a Case from Scotland

An example of ratio decidendi is the case of Donoghue v. Stevenson (1932), otherwise known as the “snail in the bottle case.” This case is a good ratio decidendi example because it explores the idea that a person can owe a duty of care to another person whom he can reasonably foresee will suffer effects as the result of his actions.

While the matter did not occur in the U.S., this case is a fundamental Western case because it essentially created the civil tort of negligence. It also implemented the idea that businesses owe a duty of care to their customers and should fulfill that duty or risk a lawsuit.

Background and Lawsuit

Here, May Donoghue was out with a friend at a café in Glasgow, and her friend ordered her a drink and paid for it. Unfortunately, because the glass was not clear, it was not until Donoghue had already drunk some of the contents that she discovered a decomposing snail inside of it.

Later, she became ill, and a doctor diagnosed her with gastroenteritis. Donoghue sued David Stevenson, the manufacturer of the beer, asking for £500 (about $650) in damages.

Donoghue could not sue Stevenson on the ground of breach of contract because she was not the one to buy the drink. However, even though Donoghue herself was not the customer, her lawyers argued that Stevenson breached the duty of care that he owed to his customers (in this case, Donoghue’s friend). They accused Stevenson of negligence that lead to Donoghue’s injury.

Decision and Appeal

At the time Donoghue filed her lawsuit, civil law was still fairly new. As such, the trial court dismissed Donoghue’s action, and so she appealed her case to the House of Lords. At that time, the House of Lords possessed the authority to hear appellate cases – something that has changed in recent years. Lord Atkin delivered the leading judgment, which found Stevenson responsible for the health of those who consumed his products, whether they were the ones to purchase them or not.

The House of Lords remanded the case to the original court, however Stevenson died before they could finalize the case. Donoghue received a damage award from Stevenson’s estate that was less than what she had originally demanded.

Said the Court:

“The burden of proof must always be upon the injured party to establish that the defect which caused the injury was present in the article when it left the hands of the party whom he sues, that the defect was occasioned by the carelessness of that party and that the circumstances are such as to cast upon the defender a duty to take care not to injure the pursuer.

There is no presumption of negligence in such a case as the present, nor is there any justification for applying the maxim res ipsa loquitur. Negligence must be both averred and proved. The appellant accepts this burden of proof and in my opinion she is entitled to have an opportunity of discharging it if she can. I am accordingly of opinion that this appeal should be allowed, the judgment of the Second Division of the Court of Session reversed and the judgment of the Lord Ordinary restored.”


Donoghue v. Stevenson may seem like a small case, but it went on to establish many important legal precedents and principles that courts still follow to this day – including negligence as a tort, and the concept of a duty of care.

It also established the “neighbor principle,” which extends negligence past the parties to a contract, including the contract’s “neighbors,” or others who may become affected by it. In this case, while Donoghue was not a party to the contract, because she did not buy the drink, she became a “neighbor” to it by consuming the product of the contract.

Related Legal Terms and Issues

  • Damages – A monetary award in compensation for a financial loss, loss of or damage to personal or real property, or an injury.
  • Jury – A group of people sworn to render a verdict in a trial, based on evidence presented.
  • Legal Brief – A written legal argument outlining the reasons for the lawsuit or appeal based on laws, regulations, case precedents, and other factors as they apply to the case.
  • Negligence – Failure to exercise a degree of care that another reasonable person in the same circumstances would take.
  • Trial – A formal presentation of evidence before a judge and jury for the purpose of determining guilt or innocence in a criminal case, or to rule in a civil matter.