While photos of the slain Lin family and their murderer Robert Xie have been splashed on the front pages of Sydney newspapers for years, the police officer who led the investigation has been content to stay in the background.

Detective Sergeant Maree was a permanent fixture in King Street court three, sitting on the hard, wooden pews in the public gallery day after day.

As Xie's lengthy committal hearing turned into two aborted trials, a third trial with a hung jury, and a six-month retrial, the years of strain on Detective Sergeant Maree were only just visible in his fatigued posture.

During the jury's deliberations this week, Detective Sergeant Maree sat upstairs in the courthouse, giving only a nod, or a polite smile to those involved in the case as he walked by.

After the guilty verdicts were delivered on Thursday, Detective Sergeant Maree quietly slipped out of court, avoided swarms of media, and walked up an alcove onto the street.

A senior NSW Police officer told Fairfax Media that is typical of Detective Sergeant Maree.

"He's very, very quiet. I've never seen him, or heard of anyone seeing him, getting stressed or worried or concerned by anything," the officer said.

"He's got a Buddhist monk thing about him.

"He's an enigma, he's a legend, his steely resolve is how the Xie case got to the end."

The pressure on investigators to find the Lin family killer was immense.

For months after the battered bodies of Min Lin, his wife Lily, her sister Irene, and the Lins' young sons Henry and Terry were found in their beds in July 2009, police did not have any strong leads, looking to China for possible mafia links.

Detective Senior Constable Martin Wilson told the second trial that Xie was acting strangely soon after the murders, making jokes about hospital paintings while his family mourned, pointing out a BMW he'd like to buy, and demanding the keys to the Lin family's busy newsagency in North Epping.

Detectives began to focus on Xie in early 2010, and brought his wife Kathy Lin before the NSW Crime Commission.

Investigators strategically tipped off Ms Lin about the discovery of bloody shoe prints at the home where her brother and his family were beaten in their beds.

Video surveillance set up in Xie's home soon captured him cutting up shoe boxes, soaking the cardboard in water, and flushing it down the toilet.

Detectives also found a small stain in Xie's garage, which a Crown forensic expert said was blood matching at least four of the victims.

Xie was arrested in 2011, and has always maintained his innocence.

There were many questions Xie's defence raised: How did one man kill five people in the dark? Why would Xie kill the nephews he loved so much?

During several bail applications over the years, magistrates and judges questioned the strength of the Crown case, which drew on motives of jealousy, rage, and sexual desire Xie had for a young person.

It seemed as if the court proceedings would never end, but Detective Sergeant Maree endured.

Detective Sergeant Maree's colleague said: "Had it been anyone else in charge ... I don't think they would have made it to the end."