No jail sentence will ever be long enough for the family of slain Sydney police officer Constable Bill Crews.

But there was relief as well as sorrow in the NSW Court of Criminal Appeal on Wednesday when the man held responsible, Philip Nguyen, had his minimum jail sentence increased by six years.

The 26-year-old trainee detective's family was devastated last March when Nguyen, 58, was jailed for at least seven years in the Supreme Court.

Nguyen did not fire the fatal shot, but he pleaded guilty to manslaughter on the grounds of excessive self-defence and to wounding Const Crews with intent to cause grievous bodily harm.

Nguyen, a drug dealer, fired at a group of police officers during the raid in the car park of his Bankstown unit on September 8, 2010, hitting Const Crews in the arm.

The constable fired three shots in return before a fellow detective fired once, accidentally fatally shooting Const Crews in the neck.

"The unusual, even unique, factual circumstances in this case have presented me with a challenging sentencing exercise," sentencing judge Justice Elizabeth Fullerton said as she handed down a maximum term of nine-and-a-half years.

But the Director of Public Prosecutions (DPP) appealed the sentence on several grounds, including that it was manifestly inadequate.

The three appeal judges agreed, finding Nguyen had "little operating in his favour" beyond his guilty pleas and expressions of remorse.

"He could not claim the immaturity of youth as a factor in the commission of these offences," the judgment said.

"In his early 50s, he had served a period of imprisonment for a serious drug supply offence. He had recently completed his parole period.

"Having not been deterred from crime, he continued to be involved in drug activity and had armed himself, with the tragic and disastrous consequences which came to pass on the evening of September 8, 2010."

The appeal judges found nothing less than a minimum sentence of 13 years would be appropriate, and they set a maximum term of 17 years and two months.

Const Crews' mother wept and family members embraced after the decision was handed down.

Nguyen was not in court for the decision but his lawyer, Ho Ledinh, said his client was "disappointed" and might consider appealing.

Const Crews' father Kelvin Crews said he felt "relief and sorrow" when the fresh sentence was handed down.

"The final sentence will never be enough," Mr Crews told reporters as he stood outside court beside his tearful wife, Sharon Crews.

"But justice has been seen to be done.

"We've had a long road these past three years and we still have the inquest to come, but we are very appreciative of the support we've been given."

NSW Police Minister Michael Gallacher also welcomed the increased sentence, noting Const Crews' death was a "senseless loss of life".

Taking into account time already served, Nguyen will be eligible for release in September 2023 when he is 68 years old.