Mrs. Donoghue visited a café in Paisley, Scotland, with a friend. Her friend purchased a bottle of ginger beer manufactured by Stevenson for Mrs. Donoghue. The bottle was made of dark opaque glass, making it impossible to see the contents clearly.

After consuming part of the ginger beer, Mrs. Donoghue poured the remainder into her glass and discovered the decomposed remains of a snail. She claimed to have suffered shock and gastroenteritis as a result of consuming the contaminated drink.

Mrs. Donoghue could not sue in contract because she had not purchased the drink herself - her friend had bought it for her. She therefore sued the manufacturer in tort for negligence, seeking damages for her illness and shock.

Lord Atkin, delivering the leading judgment, established the neighbor principle with his famous statement: "The rule that you are to love your neighbor becomes in law, you must not injure your neighbor." The court's reasoning included:

• The manufacturer had control over the product until it reached the consumer in the same condition
• The opaque bottle prevented intermediate inspection, making the manufacturer solely responsible for the product's safety
• The manufacturer could reasonably foresee that carelessness in the manufacturing process could harm the ultimate consumer
• Public policy requires that manufacturers be held accountable for defective products that cause harm

The court rejected the argument that the absence of contractual privity barred the claim, establishing that tort duties can exist independently of contractual relationships when there is sufficient proximity and foreseeability of harm.

Donoghue v. Stevenson is one of the most important cases in the common law system. Its significance includes:

• Foundation of Modern Negligence: Established the general principle of negligence that applies across all areas of tort law
• The Neighbor Principle: Created the test for determining when a duty of care exists, based on reasonable foreseeability and proximity
• Consumer Protection: Provided legal recourse for consumers harmed by defective products
• Separation of Tort and Contract: Demonstrated that tort duties can exist independently of contractual relationships
• Global Influence: The neighbor principle has been adopted by courts worldwide and remains the foundation of negligence law

The case marked the beginning of the modern law of negligence and established principles that continue to guide courts in determining liability. It is studied in law schools globally and cited in countless subsequent cases.