CAIRNS father of two Balwinder Singh Ghuman will be 73 years old before he has a chance to breathe free air again.

A  jury today found Ghuman guilty of the murders of his wife Manjinderjit Kaur Ghuman and her mother Sukwinder Kaur in 2016.

Ghuman, 46, expressed no emotion at the verdict delivered shortly after noon in Cairns Supreme Court today.

Through a Punjabi interpreter, Ghuman told the court he should not be sentenced because "I wasn't mentally fit at the time."

He was jailed for life and will spend a minimum of 30 years in prison.

The jury spent three-and-a-half hours in deliberation before finding Ghuman guilty of two counts of murder, one of attempted murder and one of unlawful wounding.

During a week of evidence, the court heard the arranged marriage of Balwinder and Manjinderjit had been troubled by his heavy drinking, paranoid delusions and resentment towards her family.

The spark that ignited the brutal inferno was Manjinderjit's demand that Ghuman leave the family home.

Fuelled by a bottle of vodka, Ghuman lost control in a frenzied bloody moment that saw Manjinderjit and Sukwinder stabbed more than 20 times each.

The prolonged horrific episode was so ferocious that a piece of the kitchen knife that Balwinder wielded broke off in his wife's face.

During the trial Ghuman did not react to the evidence against him nor did he show any emotion when he testified in his own defence.

Defence psychiatrist Dr Ian Curtis said Ghuman's lack of emotion while he was in custody for the stabbings was indicative of his poor mental health and supported his diagnosis of paranoid schizophrenia.

But Justice Jim Henry found that there "was no apparent connection" between the delusions that Ghuman was suffering and the day in question.

"The sad reality of human affairs is that the savage killings of loved ones or family members can be caused by an emotional or drunken response to rejection,'" Justice Henry said.

"(My) impression overall is that you are not a particularly sophisticated reasoner - that even without paranoid schizophrenia you did not have a particularly robust psyche and were not well equipped to think philosophically how to cope with the end of your domestic existence."

He said Ghuman's acts had been "catastrophic" to his family.

"You deprived your daughters of their mother forever, you deprived you father in law of his daughter and his wife," Justice Henry said.

"You inflicted unimaginable grief."

Ghuman's last act before walking to the cells was to speak with his lawyer.

He did not look at his daughters - then or at any time during the trial.