Indefinite imprisonment or indeterminate imprisonment is the imposition of a sentence by imprisonment with no definite period of time set during sentencing. It was imposed by certain nations in the past, before the drafting of the United Nations Convention against Torture (CAT). The length of an indefinite imprisonment was determined during imprisonment based on the inmate's conduct. The inmate could have been returned to society or be kept in prison for life. In theory, an indefinite prison sentence could be very short, or it could be a life sentence if no decision is made after sentencing to lift the term. In many cases, either a minimum term is imposed or the maximum that can be served is the maximum allowable by law in the jurisdiction for the particular offense. Incapacitation (penology) The main reason for imposing indefinite (as opposed to fixed) sentences is to protect the community. An offender can then be kept behind bars until it is determined the offender would not pose any danger to society. In some places, indefinite sentences have been around for a long time. In other jurisdictions, they have been introduced more recently. Queensland's Dangerous Prisoners (Sexual Offenders) Act 2003 authorised the continued detention of sex offenders who had served their term of imprisonment. The other Australian states followed with similar legislation. An offender who is at least 17 years of age and has been convicted of at least two violent or sexual offences can be declared a dangerous offender and detained indeterminately. A judge must consider the potential of future harm that could be caused by the offender, the circumstances of the offenses, medical and psychiatric opinion, and any other matters of relevance. The decision passed by the court is not reviewable; the indeterminate sentence(s) commence upon the expiration of any determinate sentence imposed, and release is only by way of an order from the Supreme Court. Seven Tasmanian offenders are serving one or more consecutive sentences of indefinite imprisonment as of July 2012.