A man has been charged over the family law court bombings and murders in Sydney in the 1980s, a series of attacks considered some of the city's biggest unsolved crimes.

The attacks, between 1980 and 1985, targeted judges of the Family Court of Australia, their families, a lawyer and members of the community, police said, killing four people.

Family Court judge David Opas was shot outside his home, another judge was injured by a bomb at his home, and another bomb killed Pearl Watson, the wife of Judge Ray Watson.

Another victim, Stephen Blanchard, was shot and Jehovah's Witness minister Graham Wykes was killed by a bomb at a church hall.

Three years ago, detectives attached to the State Crime Command's homicide squad restarted an investigation into the crimes.

On Wednesday morning, Strike Force Reddan detectives, helped by officers from the Tactical Operations Unit, arrested a 68-year-old man at Campbelltown.

The ABC understands the man is Leonard John Warwick, a person of interest during the investigations.

Sorry, this video has expired An ABC TV report from 1987 shows the destruction

He was taken to Narellan Police Station where he was charged with numerous offences, including four counts of murder and attempted murder.

He was refused bail to appear at Campbelltown Local Court on Thursday.

"The evidence that we've gathered includes significant new evidence, historic evidence enhanced using technology not available 30 years ago, witness evidence that was historic and new witness evidence," Deputy Commissioner Nick Kaldas said.

"The tenacity of the detectives involved, the professionalism and commitment that's been shown by the team, led by detective inspector Pam Young, has been outstanding."

Detective Superintendent Mick Willing said it was the culmination of three years of hard work.

"Three years is a long time, but as the deputy said these cases go back over 30 years, and the message is that we won't give up and we will keep working on these matters," he said.

He said family members of those killed were notified on Wednesday morning of the arrest and were "surprised and relieved".

The daughter of Judge Ray Watson, whose wife Pearl was killed in a bomb blast, said the arrest was a relief.

"I'm just very, very grateful that they have finally arrested someone," she said.

"I'm still in a state of shock and I'm totally churned up inside, but in a way I'm very, very relieved and I think it's about time the person concerned was brought to justice.

"I'm just terribly, terribly sorry that my father, who died about four years ago, is not around to see that justice will finally be done for the loss of his wife and my beautiful step-mother."

The remains of the Jehovah's Witness church hall following the bombing. ( ABC News )

Author and journalist Debi Marshall was part of an investigation by the Seven Network's Sunday Night program into the attacks.

She said the arrest would bring some closure and justice to the families and victims.

"If those families were in front of me right now I would give them a huge hug," she said.

The Chief Justice of the Family Court, Diana Bryant, said in a statement she was grateful police had "at last made an arrest after so long without any resolution of these crimes".

She declined to make any further comment "until the judicial process has been concluded".

Dozens of officers have been searching Mr Warwick's large, semi-rural property at Douglas Park, and appear to be sifting through the contents of his home, garage and a big shed.

Among the items being examined by clothed and uniformed police are a boat, at least one vehicle and numerous boxes strewn across the property's lawns.

In 1984, police offered a $500,000 reward for information about the attacks.