The wife of murdered Detective Inspector Byrson Anderson says today's sentencing of her husband's killers brings little comfort.

Mitchell Barbieri, 21, broke down in the NSW Supreme Court as he was sentenced to at least 26 years in prison for fatally stabbing Det Insp. Anderson in December 2012.

His mother Fiona Barbieri, 47, was given a minimum seven and a half years behind bars for the manslaughter of the officer.

"Today's decision is not the outcome we believed would be achieved in the days and the months following Bryson's murder and we're all disappointed by that fact," widow Donna Anderson told media outside court today.

"I would have thought there is no excuse for killing a police officer."

Mitchell Barbieri escaped the mandatory life sentence reserved for the killing of police officers; Justice Robert Allan Hulme accepting that Barbieri was suffering from a delusional disorder "transferred" from his mother at the time of the crime.

Justice Hulme acknowledged the elder Barbieri had fostered an environment at home, where her late-onset paranoid schizophrenia had influenced her son.

Donna Anderson addresses media after the sentencing of her husband's killers.

"These two people have demonstrated that they are not fit to be in the community at large," Ms Anderson told A Current Affair. "Who's accountable for them if they are released? I think that is a huge concern."

Det Insp Anderson died after being stabbed several times while making a visit to the Barbieri's Oakville property in Sydney's northwest, following reports the younger Barbieri had been shooting arrows at his neighbour.

The pair had barricaded themselves inside their home when police arrived, screaming at authorities to "f--- off, you're not invited."

Meanwhile inside the house, the pair sent emails to a host of politicians declaring their right to defend themselves and their property.

Bryson Anderson. (Nine News)

Det Insp Anderson was fatally attacked by Barbieri when he tried to access the home from the back door.

"He plunged a hunting knife deep into the officer's chest, causing virtually immediate death," Justice Robert Allan Hulme said of Barbieri.

"In doing so he acted with an intention to kill him."

Armed with hammer, Barbieri's mother also lashed out at officers who were trying to subdue her son.

In sentencing the pair, Justice Hulme said while the Barbieri's regretted what had happened, he wasn't persuaded that either was genuinely remorseful as they had not accepted responsibility.

"I don't feel anything towards them and I say that honestly. Time that I think about them is time I am not thinking about Bryson" Ms Anderson told A Current Affair.

"He was 45 years' worth of wonderful experiences and humour and love and that's what I want to be talking about when we're talking about Bryson and not for the focus to be on these two people or on the court matter."

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