Let’s break down these cases and sources of law so you can weaponize
them for your exam! Knowing the name of a case is good, but knowing
why the court made its decision (the ratio decidendi) and how to apply it
to a problem question is what gets you the distinction.
Here is your exam-focused interpretation of every major case and statute
from your materials.
1. The Mistake & Reliance Heavyweight
Case: Sonap Petroleum (SA) (Pty) Ltd v Pappadogianis
The Core Principle: This is the ultimate authority on the Reliance
Theory. It dictates what happens when one party makes a material
mistake (like putting the wrong plot of land in a contract) and the
other party tries to hold them to it.
How to use it in an exam: Use Sonap whenever a set of facts
involves a misunderstanding or a typo in a contract. You must
apply the "three-fold test" to see if the mistaken party is still
bound. The secret weapon here is "snatching at a bargain." If
your exam facts show that Party B knew Party A made a mistake
but quickly signed anyway to get a good deal, cite Sonap to argue
that Party B's reliance was unreasonable, meaning the contract is
void.
, 2. The Advertisement Rule
Case: Crawley v Rex
The Core Principle: An advertisement or a price tag in a shop
window is an invitation to do business, not a binding offer.
How to use it in an exam: If a problem question features a
customer seeing a flyer, an ad (like the "Green Mamba" security
ad), or a price tag, and saying "I accept!", cite Crawley v Rex.
Explain that the customer is actually making the offer to buy, and
the shop owner/company has the right to accept or reject it.
3. The Abuse of Trust Case
Case: Preller v Jordaan
The Core Principle: This case firmly established Undue
Influence as a separate ground to set aside a contract in South
African law.
How to use it in an exam: Look for facts involving a power
imbalance—like a doctor/patient, lawyer/client, or a caretaker and
an elderly person. If the stronger party uses their influence to get
the weaker party to sign a prejudicial contract (like giving away a
farm), use Preller v Jordaan to list the four requirements and
conclude that the contract is voidable.
them for your exam! Knowing the name of a case is good, but knowing
why the court made its decision (the ratio decidendi) and how to apply it
to a problem question is what gets you the distinction.
Here is your exam-focused interpretation of every major case and statute
from your materials.
1. The Mistake & Reliance Heavyweight
Case: Sonap Petroleum (SA) (Pty) Ltd v Pappadogianis
The Core Principle: This is the ultimate authority on the Reliance
Theory. It dictates what happens when one party makes a material
mistake (like putting the wrong plot of land in a contract) and the
other party tries to hold them to it.
How to use it in an exam: Use Sonap whenever a set of facts
involves a misunderstanding or a typo in a contract. You must
apply the "three-fold test" to see if the mistaken party is still
bound. The secret weapon here is "snatching at a bargain." If
your exam facts show that Party B knew Party A made a mistake
but quickly signed anyway to get a good deal, cite Sonap to argue
that Party B's reliance was unreasonable, meaning the contract is
void.
, 2. The Advertisement Rule
Case: Crawley v Rex
The Core Principle: An advertisement or a price tag in a shop
window is an invitation to do business, not a binding offer.
How to use it in an exam: If a problem question features a
customer seeing a flyer, an ad (like the "Green Mamba" security
ad), or a price tag, and saying "I accept!", cite Crawley v Rex.
Explain that the customer is actually making the offer to buy, and
the shop owner/company has the right to accept or reject it.
3. The Abuse of Trust Case
Case: Preller v Jordaan
The Core Principle: This case firmly established Undue
Influence as a separate ground to set aside a contract in South
African law.
How to use it in an exam: Look for facts involving a power
imbalance—like a doctor/patient, lawyer/client, or a caretaker and
an elderly person. If the stronger party uses their influence to get
the weaker party to sign a prejudicial contract (like giving away a
farm), use Preller v Jordaan to list the four requirements and
conclude that the contract is voidable.
