Johnston v The Queen

The appeal before the High Court involved the applicant, Johnston, who was convicted in the Supreme Court of Queensland for engaging in sexual intercourse with three children aged between 14 and 16. The legal issue at the heart of the case was whether the applicant's guilty pleas, entered when the existing law was that such acts constituted a criminal offence, could be sustained following a change in the law that abolished the offence of sexual intercourse with a child aged between 14 and 16. The central legal issue was whether the applicant's pleas were invalid in light of the subsequent legislative amendment.

The High Court found that a miscarriage of justice had occurred. The Court held that the applicant's pleas were entered in reliance on the existing law, and when the law was altered, the pleas became invalid. The Court emphasised that the validity of a plea depends on the state of the law at the time it is entered, and if the law changes after the plea is entered, but before the sentence is passed, the plea is no longer valid. The Court held that the applicant's convictions could not stand as they were based on invalid pleas. The Court concluded that a miscarriage of justice had occurred as the applicant had been convicted and sentenced on the basis of pleas that were no longer valid under the altered law.

The High Court quashed the applicant's convictions and ordered a retrial, or alternatively, that the applicant be discharged if the Director of Public Prosecutions decided not to proceed with a retrial. The Court found that the applicant had not had a fair trial as the convictions were based on invalid pleas. The Court held that the miscarriage of justice established by the invalid pleas entitled the applicant to be discharged unless the Director of Public Prosecutions chose to proceed with a retrial.