Do mandatory minimum sentences work?

WHAT ARE THE VICTORIAN LIBERALS PLANNING?

Titled "Taking Back Our State", their plan would give violent criminals convicted of a subsequent violent offence a minimum sentence of at least six years. The minimum for murder would go from zero to 20 years. The rape minimum would go from zero to 15 years.

Eight of the 11 offences listed don't have mandatory minimums in normal circumstances. Those that do - one-punch manslaughter (10 years), aggravated home invasion and aggravated car-jacking (both three years) - would increase substantially.

WHY NOW?

The plan comes at a time when the crime rate per capita rose by 21 per cent between 2012 and 2016.

"We need to put the victims first, rather than last, like the system does," Mr Guy says.

ARE MANDATORY SENTENCES USED ELSEWHERE?

The idea isn't new. When the death penalty was abolished, most states and territories adopted mandatory life sentences for murder.

In 1996, WA brought minimums for home invasion. In the years since, the NT, Queensland, NSW, South Australia and Victoria have followed with minimums for a variety of offences.

HOW MUCH WOULD IT COST?

The Liberals won't say but it appears they don't care how much it will cost.

"Lives are worth saving, no matter the cost," they say in the plan.

The Australian Lawyers Alliance labelled it "horrendously expensive".

It costs almost $103,000 a year to keep someone in a secure Victorian prison, the Productivity Commission said in 2015.

Mr Guy said his proposal would affect "up to three to four thousand over a period of time".

DOES MANDATORY SENTENCING WORK?

Victoria's sentencing advisory council and the Australian Law Council argue no.

A 2001 the WA government review of home invasion minimums concluded they'd had "little effect on the criminal justice system".

Asked if there was an evidence for his plan, Mr Guy cited California and "other areas of North America" but did not go into more detail.

Sources: NSW Parliament Research Service, Sentencing Advisory Council Victoria, Victorian Opposition, Australian Law Council, Crime Statistics Agency Victoria, Australian Lawyers Alliance