R v McMahon; Ex parte

The applicants, R and McMahon, sought a writ of prohibition against the respondent, the Commonwealth, to prevent the prosecution of McMahon for offences under the *Crimes Act 1914* (Cth). The dispute concerned the validity of the prosecution, which was initiated by the Commonwealth Director of Public Prosecutions (CDPP) following an investigation by the Australian Federal Police (AFP). The matter came before the High Court of Australia.

The central legal issue before the High Court was whether the CDPP had the power to prosecute McMahon for the alleged offences, specifically in light of the fact that the investigation had been conducted by the AFP and the prosecution was being brought by the CDPP. This raised questions about the scope of the CDPP's prosecutorial discretion and the relationship between the AFP's investigative powers and the CDPP's power to institute and conduct prosecutions.

The Court considered the provisions of the *Director of Public Prosecutions Act 1983* (Cth) and the *Crimes Act 1914* (Cth). It was held that the CDPP had the statutory authority to institute and conduct prosecutions for offences against the laws of the Commonwealth, irrespective of whether the investigation was conducted by the AFP or another body. The Court reasoned that the CDPP's discretion in deciding whether to prosecute was broad and not fettered by the source of the information or the investigative agency. The applicants' arguments that the prosecution was an abuse of process or otherwise invalid were rejected.