It was held by the High Court of Australia in 3-1 majority that, in all the circumstances, it was unconscionable for the bank to rely on the guarantee. Notable circumstances taken into the account by the court include:
The Amadios had a limited understanding of English.
The Amadios did not have the benefit of independent advice, and such advice was not provided or suggested by the bank.
When the mortgage was executed the bank was aware of the Amadios' son's financial situation and knew the Amadios were not so appraised.
The bank did not advise the Amadios that there was no limit on their liability under the guarantee - the Amadios believed the liability was limited to $50,000.