Justice Peter Garling, who heard the Supreme Court trial without a jury, on Monday reserved his decisions on former firefighter Leonard Warwick.

The 73-year-old has pleaded not guilty to four murders and 20 other offences related to seven events that occurred in Sydney between February 1980 and July 1985.

The Crown opened the trial in May 2018 and the case occupied more than 200 hearing days.

But the trial was also beset by repeated delays, applications and adjournments primarily related to the funding of Warwick's defence after he became penniless.

Prosecutor Ken McKay has contended the seven events were "inextricably linked" to drawn-out Family Court proceedings involving Warwick and his ex-wife Andrea Blanchard, which ran from 1979 to 1986.

Four events were said to have directly related to their Family Court hearings.

They were the shooting murder of Justice David Opas, the bombing of Justice Richard Gee's home and of the Family Court building in Parramatta, and the bombing of the home of Justice Ray Watson in which his wife Pearl was killed.

The three judges had made orders adverse to Warwick, while his cases were heard at Parramatta - the only Family Court registry to be bombed in Australia.

Those events were "book-ended" by events of serious violence which were related to Ms Blanchard - the shooting murder of her brother Stephen and a car bomb at the previous home of her solicitor, according to the Crown.

The final event was a bomb which ripped apart a Jehovah's Witnesses hall, killing Graham Wykes and injuring 13 other members of the congregation offering support to Ms Blanchard.

"He is circumstantially linked to each crime," said Mr McKay's offsider Gareth Christofi.

"The Crown submits the circumstances in which the seven events occurred are substantially similar - the intended targets had involvement in the marital dispute in a way which was adverse to the accused's interests."

The Crown also relied on evidence which it said indicated Warwick had the knowledge and skill to make an improvised explosive device and DNA evidence found on cardboard and carpet in the bombed hall.

But Warwick's solicitor, Alan Conolly, argued two of the events - Mr Blanchard's murder and the car bomb - had nothing to do with the Family Court.

He suggested Warwick's brother-in-law's death related to drugs, while the car bomb was placed outside a "party" residence from which Ms Blanchard's lawyer had moved out months ago.

He criticised the "hopeless" investigation conducted by police, referred to a number of other suspects and described the Crown case as "a gossip club".

The truth was that his client and his ex-wife had a "cordial relationship" and worked through their matters "very successfully", he said.

Mr Conolly said the problem the Family Court was having at the time was not with "a" litigant.

"It was with a group of men who could be identified, who publicly announced their hatred of the court and some were free to say what they would do about it," he said.

The bombings were likely to have been orchestrated by these angry men, who probably contracted it out.

"The thesis that it was one man is trite nonsense."

Australian Associated Press