Max Sica's family say they are looking forward to fighting his triple murder conviction, after his acquittal on child sex charges.

A Queensland judge on Friday found Sica not guilty of 21 charges including maintaining a sexual relationship with a child, rape, carnal knowledge and indecent dealing.

The 42-year-old had been accused of having a four-year sexual relationship with a girl that started when she was nine.

Sica is serving a 35-year jail sentence for murdering his 24-year-old ex-girlfriend Neelma Singh and her younger brother and sister in their north Brisbane home in 2003.

His family maintain he was wrongly convicted of the Singh sibling murders in 2012 and are looking forward to appeal hearings in May.

Outside the District Court in Brisbane, Sica's brother said the acquittal was proof police had invented the child sex charges to prejudice Sica's murder trial.

Claudio Sica maintains there is forensic evidence someone else killed the Singhs and corrupt police set his brother up.

"Justice has finally been served but not fully," Claudio Sica told reporters.

"The jury (in the murder trial) obviously did not do their job."

Earlier, a smiling Max Sica turned and waved to supporters in the court's public gallery after the judge pronounced him not guilty.

He had been on trial since November after several delays in the case.

Sica was granted a judge-only trial after his lawyers successfully argued the publicity surrounding his murder hearings would prejudice a jury.

In police video shown during the trial, the complainant, who is now 17, is seen telling detectives Sica had been a family friend and they'd had sex about 100 times.

The sex had occurred mostly at his Brisbane home between 2004 and 2008 and she'd fallen in love with him.

There were no independent witnesses, and it was the results of a medical examination presented by defence barrister Sam Di Carlo that ultimately saw Sica acquitted.

The examination of the child at 13 showed an intact hymen - a state that was highly unlikely if her claims were true, according to a doctor who specialises in sexual assault and who appeared for the defence.

In a written explanation of his verdict, Judge Michael Shanahan said the evidence didn't support the girl's account of repeated sexual penetration from age nine.

"As this is fundamental to the prosecution case and has a significant impact on the complainant's credibility, I am left with what, to my mind, is a reasonable doubt about the guilt of the accused," he wrote.

A hearing to appeal Sica's murder conviction is set for May 27.

In 2012 he was found guilty of killing Neelma Singh, her 18-year-old brother Kunal and 12-year-old sister Sidhi in their home in Bridgeman Downs.

A jury agreed with police that Sica strangled Neelma, beat her siblings with a garden fork because they were witnesses, and dumped all three in a spa.