In Western Australia, drink driving penalties depend on the blood alcohol concentration (BAC) level, with lower BACs resulting in fines and demerit points, while BACs of 0.08 or higher lead to automatic disqualification and court attendance. First-time offenders face fines ranging from $150 to $900 and varying disqualification periods based on their BAC. Subsequent offences incur higher fines, longer disqualifications, and may include participation in an interlock program for offenders with multiple convictions within a five-year period.