Reports of family violence increased by more than 50 per cent during his time, from 40,778 in the financial year before his November 2011 appointment to 65,393 in 2013-14.

Family violence accounts now for almost half of the reported "crimes against the person", with 21,447 reports of assaults - almost 60 a day - recorded in the past financial year. Some of these were threats to kill or injure, which have become one of the fastest-growing offences in the past decade.

But the numbers do not necessarily mean family violence has become more prevalent. Mr Lay has been a prominent voice in bringing the issue into the open, and police have been urging more people to come forward. The effect might be that more people feel safe to report family violence, which can only be a positive sign despite the rising number of offences.

A growing challenge of family violence has been intervention order breaches and repeat offenders. In 2013-14, the number of family violence intervention order breaches and other justice procedure offences reported to police outstripped assaults for the first time.

A Fairfax Media analysis earlier this year found one in five people subject to an order in 2012-13 breached it, with 820 people - overwhelming men - breaching them at least three times.

The role of family violence in homicides has also been brought into the spotlight. Earlier this year police admitted the number of domestic violence-related homicides had been understated. During Mr Lay's tenure, police have acted to reclassify past offences to indicate family violence was a factor.

This has happened as police made the drug ice a more prominent target. In the year before Mr Lay took over as chief commissioner there were 626 offences statewide involving ice usage, possession or trafficking.

By 2013-14 this had surged sixfold to 3752 and methamphetamine had become the second-most common illicit drug in the crime statistics behind cannabis.

Ice makes up 16 per cent of drug crime now, compared with 4 per cent in 2010-11.

Again, the increase in offences also reflects increased police resources directed at the drug, particularly trafficking.

But drugs and family violence are not separate issues, with Victoria Police's recent annual crime statistics publication showing the two problems are increasingly related.

In 2013-14, drugs were a factor in 6482 family violence incidents, compared with 2468 in 2010-11. Police also suspected drugs were a factor in 16,434 other such reports, up from 8593 in 2010-11.

Altogether it means drugs were a likely factor in almost 23,000 family violence reports, compared with 29,000 in which alcohol was confirmed or suspected.

Family violence and ice will also  be a big focus for Mr Lay's successor.