William Tyrrell's foster family has blasted the "personal agendas" of police behind the prosecution of former detective Gary Jubelin, saying the investigation into the boy's disappearance has been "cavalier" following his removal.
Jubelin is defending four charges of illegally recording elderly neighbour Paul Savage during an investigation into the 2014 disappearance of the three-year-old from NSW's mid-north coast.
Mr Savage, 75, denies any involvement in William's disappearance.
Outside court on Friday, a spokeswoman for the family detailed their "grave concerns" over the investigation's mismanagement since Jubelin was stood down in 2019.
"We hold deep fears for those families coming behind us and question how they might trust senior police to put their personal agendas, ambitions and bias aside to focus on solving these horrendous crimes," Alice Collins said.
"There needs to be greater transparency and accountability within NSW Police which can only be achieved through institutional change."
The comments follow a 10-day hearing into Jubelin's alleged offending which aired a number of difficulties and internal tensions during the probe.
Jubelin claimed then-homicide commander Superintendent Scott Cook in 2017 said "no one cares" about William.
The boy's foster mother said Supt Cook made similar remarks to her in 2019.
Supt Cook denies the accusation and Commissioner Mick Fuller this week released a statement supporting him as "exemplifying the definition of a leader".
Jubelin claims the recordings he made were lawful as they were made to protect himself in the event Mr Savage made a complaint or self-harmed and his colleagues didn't defend him.
His barrister, Margaret Cunneen SC, used her closing address on Friday to argue statements Mr Savage made during the proceedings - which contradicted the tapes of the conversations - and testimonies from former colleagues with an "axe to grind" were evidence of the interest Jubelin had in making the recordings.
Jubelin had proved himself an honest man and Mr Savage's privacy had already been taken away by the NSW Supreme Court through surveillance warrants, Ms Cunneen said.
"This is the prosecution of a fine servant of our state over many, many years with many successes on his record," she told Downing Centre Local Court.
She said Jubelin's prosecution was an extraordinary attack on "a veteran homicide investigator with a totally unblemished record as a police officer who, if he has committed an offence, has done so in the dogged and determined and professional exercise of his duty".
But prosecutor Philip Hogan said that was an excuse Jubelin came up with after finding himself in hot water over his "entirely improper inquisition on a vulnerable old man".
Jubelin violated Mr Savage's rights in circumstances where he didn't care if he was breaking the law or not, he said.
Mr Hogan accused Jubelin, 57, of making speeches instead of answering questions, avoiding responsibility for his actions, shifting blame and being untruthful.
A decision to find Jubelin had a legitimate interest in recording the conversation would render "comprehensive frameworks" around privacy and police surveillance "completely useless", the prosecutor said.
"The defence that has been asserted simply doesn't exist. No individual police officer is above the law."
Magistrate Ross Hudson reserved his decision until April 6.
Jubelin - who quit the force in 2019 - told reporters outside court he held no animosity towards NSW Police but was frustrated William hadn't been found.
"I look at the resources that have been put into prosecuting me and I just can't help but think that would have been better if those resources were put into finding out what happened to him."
Australian Associated Press