Strict liability is very rare in common law offences. Outraging public decency is a strict liability common law offence. About half of all statutory offences are strict liability. The courts start by assuming that mens rea is required, but are prepared to interpret the offence as one of strict liability if Parliament has expressly, or by implication, indicated this in the relevant statute. The modern judicial attitude is to avoid interpreting offences as strict liability. In the Gammon (Hong Kong) Ltd v A-G of Hong Kong, the Privy Council set out five factors to be considered, one of which was that there is a presumption that mens rea is required before a person can be guilty of a criminal offence. The justification of strict liability is that it protects society by promoting greater care over matters of public safety.