He's putting that experience to good use, in charge of eight police districts from Wollongong to the Victorian border.

Assistant Commissioner Joe Cassar's days are filled with finding ways to make sure the police commands within his jurisdiction are "match fit".

That includes ensuring the commanders in the Southern Region have the resources to respond to public calls for assistance, reduce crime rates and importantly, he makes sure his police officers are okay.

In July, Mr Cassar was promoted to the role after 32 years in the force.

Now he gets to be the boss of the region he calls home and where he has spent most of his career.

In his long and distinguished service, Mr Cassar has seen it all.

He has worked in regional areas, intelligence, as a detective at Port Kembla, in the major crimes, drug and child abuse units.

But most of his time was spent in the homicide squads in Sydney and the Illawarra.

"I worked on quite a large number of homicide cases," Mr Cassar said.

He said one of the more infamous cases he worked on was seeing Mark Valera, convicted in 2000 of the murders of former Lord Mayor Frank Arkell and David O'Hearn in Wollongong.

Less than two weeks after Valera was sentenced to life without parole, Mr Cassar, who at the time was a detective, also helped solve the murder of Valera's father Jack van Krevel.

Police discovered that Valera's sister Belinda van Krevel, had 'asked' Keith Schreiber to kill their father because she blamed him for Mark's imprisonment.

Schreiber was found guilty of the murder and was sentenced to life imprisonment with a non-parole period of 12 years.

"That case has been the most intriguing," he said.

Mr Cassar said investigating the Joseph Logozzo murder at Cecil Hills in 2002 was one of the most "fulfilling" cases he worked on.

"It was a home invasion gone wrong and Joe was murdered," he said.

"The Logozzos were such a wonderful family. The two intruders were wearing balaclavas.

"The statistics say 90 per cent of offenders are known to the victim somehow.

"But this one was completely random."

Mr Cassar said the investigation was an uphill battle and police worked closely with the family.

"Over the course of the investigation, we got some good leads and we were able to identify who the offenders were," he said

"Even when we went to court is wasn't [a close and shut case].

"The way we got the confession was a little different to normal standards. We were pushing the boundaries of how we could obtain the evidence but we couldn't obtain it any other way.

"We went to court, the evidence got thrown out so it went to appeal. We got the evidence in, then we convicted him.

"Sophear Em got 46 years in jail. He took it to the High Court but we won it."

Mr Cassar said homicide units had "good strike rates" when it came to solving murders.

"Homicide is one crime that NSW Police will put an enormous amount of resources and time into until we really have no other leads to pursue," he said.

"It would only be a very small handful of cases that remain unsolved such as prostitutes who we found dead and their bodies were dumped but we couldn't say whether the prostitute had been murdered or it was a drug overdose."

However, there was one case, a two-year-old boy found dead in his Mount Druitt home, that Mr Cassar wished he'd been able to get a conviction.

"We knew the parents were responsible for it because the child had bruising around the neck," he said.

"We did everything we could and it was the forensic evidence that couldn't get us over the line.

"The tests couldn't prove whether the death had been caused by asphyxiation or chocking.

"I can sleep at night because I know we did a very professional job and we did absolutely everything we could do but there was nothing more we could do."

Becoming a police officer was Mr Cassar's dream as a young boy.

"I wanted to lock up crooks and I like working with people," he said. "When I talk to a leadership team or probationary constables, I tell them to remember the reasons why they joined the police force.

"For me, it was to lock up crooks and keep members of the public safe.

"I tell them they will have their bad days or they'll be chasing promotion but they always have to keep focused on why they joined the police. Thirty-two years later, I still remember."

Mr Cassar said he had the privilege of setting up an alcohol licence enforcement command while he was a superintendent.

Under the direction of NSW Police Commissioner Andrew Scipione, Mr Cassar was tasked with helping to change the drinking culture and reduce king hits and glassings in the state.

He worked with the Australian Hoteliers Association and Clubs NSW to change legislation. The command instigated regulations where licenced venues with a high number of assaults had conditions and restrictions put on them.

"Over the past 10 years, those measures have significantly changed the drinking culture and alcohol-related crime out there now," he said.

But what Mr Cassar feels most proud about is helping see out Commissioner Mick Fuller's vision of changing the life cycle of young offenders. He said the commissioner wanted to reduce adults re-offending and decrease the number of people in prison.

"Commissioner Fuller knew we had to do something at the local level," Mr Cassar said. "I was the Assistant Commissioner of the Capability, Performance and Youth Command in 2017... so we restructured all the youth programs to better utilise the PCYCs and introduced the RISE UP and Fit for Life programs.

"Maybe it's because I am getting older, but I think that has been a more significant contribution to NSW Police than my role in solving homicides and reducing alcohol-related crime because now I am seeing the changes.

"We have seen large numbers of participants get jobs and not commit offences. That is really going to impact their lives and the law and order systems in 10 and 20 years."

Mr Cassar said he felt "fortunate" to be in in his position.

"Where I am here and now, I don't think it gets any better," he said. "I get to run the region where I live, got married and raised my children.

"I know the area of Wollongong and I've worked in five of the eight police districts in the southern region.

"It has a lot of challenges and high levels crimes such as drug crime.

"The southern region deserves me to invest my time into it but I'll do whatever the commissioner tells me to do."