The investigation and trial over an execution-style killing more than 23 years ago was "riddled with ineptitude", says the son of a Queensland businessman found not guilty of murder.
Adam Pentland's father Neil Andrew Pentland, 72, was acquitted on Tuesday of shooting marketing manager Philip Carlyle four times in the head and neck on April 13, 1997.
Mr Carlyle's body was found in a soundproof air-conditioning plant room in the men's Robina office.
Mr Pentland was charged with murder more than two decades later.
But Brisbane Supreme Court Justice Glenn Martin has rejected the prosecution's case, saying police had failed to follow up some information early in the investigation.
This included a triple-zero call the day after Mr Carlyle's death in which a man said he had "shot a guy". By 1998 the call recording could not be recovered because it had been overwritten.
"In a circumstantial case like this, the failure to do these things places a shroud of doubt over the whole body of the investigation," Justice Martin said in his published reasons.
Adam Pentland says investigators made many negligent mistakes and failures, and the director of public prosecutions had put forward a "patently flawed case".
"The investigation and trial which concluded today is riddled with ineptitude compounded by mismanagement," he told reporters outside court.
"All lines of inquiry that did not support the case against my father were abandoned and ignored. Because of these gross errors the murderer is extremely unlikely to be held accountable."
Mr Carlyle was employed by a start-up internet company owned by Neil Pentland and his wife. He was not a shareholder, but they had agreed he could buy shares in future.
By the time he started to work with Mr Pentland, Mr Carlyle had a trail of failed businesses, disappointed investors and angry creditors.
He was a heavy gambler at times, had been threatened with violence, had moved his family fearing their safety and his wife had once been held up at knife-point over a debt.
"There were a number of people who had been identified to the police in the first chapter of the police investigation as people who had a reason to be unhappy with Mr Carlyle," said Justice Martin.
Some were only interviewed some 18 months after the murder.
Justice Martin said he did not accept the prosecution's case that the relationship between Mr Pentland and Mr Carlyle had been deteriorating enough to provide a motive.
"The material demonstrates that they had a number of disagreements ... But those disagreements were nothing more than one might expect from persons engaged in an enterprise with considerable pressure upon them and in which each saw the prospect of considerable success," the judge said.
He also found an insurance policy the two men had taken out that would pay out $500,000 if either one died wasn't a motive.
"To kill Mr Carlyle, in order to obtain the payout from the insurance policy, when, on any reasonable view of the evidence, the defendant thought that they were on the cusp of great success, makes no sense at all."