Plenty of Australian criminals know all about the persistence of detective Bob Reid.
In the 1980s, he arrested Sydney's "Mr Sin" Abe Saffron on charges of tax evasion and helped put away corrupt former deputy commissioner of NSW police, Bill Allen.
But the 16-year hunt for Ratko Mladic proved to be one of Reid's most difficult cases, and one many told him he would never solve.
Reid is the chief of operations at the International Criminal Tribunal for the former Yugoslavia (ICTY), a law court set up in 1993 to deal with atrocities committed in the Balkans wars of the 1990s.
For the last 23 years, he has helped track down and arrest over 160 war criminals and bring them to justice.
As the former Bosnian Serb army commander Mladic this week awaits his verdict in The Hague over charges of genocide and other war crimes, his victims can thank the former NSW policeman for putting him in the dock.
The military man known as "The Butcher of Bosnia" stands accused of two counts of genocide, five counts of crimes against humanity and four counts of violations against the laws or customs of war.
During the Bosnian war, he was in charge when the city of Sarajevo was shelled and under siege for close to four years and when genocide was committed against around 8,000 Muslim men and boys at Srebrenica in 1995.
For 16 years after the war Mladic remained on the run. Capturing him proved difficult because many Serbs revere him, and were happy to help protect him from the authorities.
"He was seen as a hero," said Reid from his office in The Hague.
"He was an army commander who was loved by his troops."
While Mladic's collaborator, the politician Radovan Karadzic, was able to hide undercover for 12 years by posing as a mystic faith healer, Mladic relied on his old military colleagues to protect him.
But after Boris Tadic became defence minister and then president of Serbia, things started to get more difficult for the fugitive.
Once the European Union agreed to make Serbia's future membership conditional on handing over war criminals, the noose around Mladic began to tighten.
"They cut off state-sponsored protection in military barracks, so he then had to go to what I call his comrades: retired colonels, majors, captains," Reid said.
"They were looking after him and then that was cut off too."
Reid worked closely with Tadic's national security adviser Miki Rakic, setting up a taskforce with offices in Belgrade and Sarajevo.
The taskforce put together a timeline of where and when Mladic had been seen to establish a pattern of his movements.
"There was only two things Ratko Mladic trusted in life. One was the military, the other was the family," Reid said.
With military protection cut off, his family became the primary target for the taskforce.
"We just picked off one family member after another. Then one May day in 2011, they walked through the door and he was sitting behind them."
Mladic had been arrested by Serbian forces. Reid received the news while he was running a taskforce meeting in Sarajevo.
"We'd just started the meeting and my phone rang and I could see it was the prosecutor, so I excused myself and walked out," he said.
"We only had two fugitives at that stage: number one was Mladic, and number two was [Goran] Hadzic.
"The prosecutor said, 'I've just been informed number one has been arrested', and I said, 'I think you mean number two'.
"He said, 'No, no' and I went back in. They must have thought I was drunk or on drugs because I walked back in and I just couldn't think. I was stuttering over things and they're all looking at me."
Mladic's arrest was 'the ultimate'
Official confirmation came when the president of Serbia made a televised address at lunchtime telling the nation that Mladic had finally been apprehended.
That afternoon Reid travelled with Serbian security services to Belgrade where he saw for himself that the joint taskforce had finally got their man.
"The arrest of him was the ultimate. When I came here in 1994 everybody said, 'Don't get comfortable, don't ever buy a house here because you will only be here for a couple of years, you've been set up, you'll never get a fugitive through the door'.
"In the end we indicted 161 of them. With the arrest of Mladic and then Hadzic, the tribunal that was never supposed to succeed had accounted for all 161 people who had been indicted."
NSW Magistrate Graham Blewitt was the deputy chief prosecutor of the ICTY in 1994, when he hired Reid to work as an investigator.
He's not surprised that the war crimes investigations at The Hague have been a success with Reid at the helm.
"In my view he has proven himself time and time again to be one of the world's best investigators," Blewitt said.
"His professionalism and dedication, and ability to lead others, are second to none. Bob commands the respect of everyone he works with."
'The last time this was done was Nuremberg and Tokyo'
Reid's work over the last 23 years has not been just about capturing fugitives. He has also had to gather evidence of war crimes.
That has meant securing DNA from mass graves, recording eyewitness accounts, seizing official documents and acquiring audio and video evidence.
When he took the job in 1994 he had to start from scratch.
"There was no template when we arrived here. The last time this was done was Nuremberg and Tokyo," Reid said.
"We had to be inventive, like who would have ever thought that by getting a search warrant to go and search the municipality of Prijedor we would come back with so many documents?"
Prijedor was the scene of some of the worst war crimes committed during the Bosnian War.
Thousands of Muslims and Croats were killed. Countless others were tortured and raped. Reid visited the municipality in 1996 to gather evidence for prosecutors.
On that trip he visited the site of the Room 3 Massacre at Keraterm Camp. Reid said it remains one of the worst things that he saw.
"There were hundreds and hundreds of men in there," he said.
"Whether they put tear gas in there, nobody really knew, but there was mass panic and as they burst out of the room there was a machine gun nest out the front and they just mowed them all down.
"When we did our crime scene examination, we tested for the presence of blood. We did that in February 1996. The crime occurred in July 1992. We did it about 11:30 at night and the place just lit up.
"You could even tell in some instances the type of sneaker that the individual was wearing there was so much blood on the floor."
Moving on … to the Rwandan genocide
For Reid, the most important part of the job has been helping to get justice for survivors and the families of the dead.
"There were so many crimes that took place in the war, we had five conflicts, we had Slovenia, Croatia, Bosnia, Kosovo and Macedonia, so right across the board you are always trying to bring justice for the victims," he said.
The former NSW policeman will pack up his desk soon at The Hague. The ICTY will close on December 31 after the Mladic verdict and the upcoming Jadranko Prlic appeal.
Over the next few months he's working to track down more fugitives from the Rwandan genocide.
Blewitt had predicted that his old workmate would be the one to see the war crimes tribunal's work right through to the end.
"When I left in 2004, we used to joke that Bob would be the last one out the door when the ICTY finally closed, and that Bob would be the one to turn out the lights for the last time.
"That now appears to be a reality."
Watch Lateline’s story on Ratko Mladic’s legacy at 9.30pm AEDT on the ABC News Channel and 10.30pm on ABC TV.