"It has irreparably altered the way in which they will approach life. Offending of this type robs children of their childhood," he said.
"As regards to each, you have blighted their young adulthood and indeed you have cast a shadow over their maturity and their family life."
Minnell, who served with the police between 1959 and 1965, was living in Whanganui when his offending began against victim A between 1994 and 1996.
Victim B was raped by Minnell. She eventually brought his offending to the attention of others.
Minnell took victim C on a vacation somewhere in the wider Bay of Plenty area.
"You stayed overnight. She was watching a movie, you came in and (sexually assaulted her)," Judge Crayton said.
"She told you not to touch her like that ever again. Your response was to laugh at her."
Following the trip away, Minnell maintained contact with victim C, without her mother's knowledge.
"She had a difficult and unfortunate home life. Your contact gave her assistance, it provided her with some comfort that was not available through her family," Judge Crayton said.
"She would visit you, she would watch the television, she would on occasion have something to eat. You made it clear that you expected a reciprocation for your support."
Victim C was able to cut ties to Minnell in 2006 when she formed a sympathetic and supportive relationship and left Whanganui.
Minnell was found guilty on 11 charges of sexual violation by unlawful sexual connection, three charges of doing an indecent act on a girl under 12, four charges of indecently assaulting a girl under 12 and one of sexual violation by rape.
Two of the complainants watched the proceedings from the public gallery and declined the opportunity to read their victim impact statements in court.
In sentencing Minnell, Judge Crayton took into account his age and previous good character.
"You did until the age of about 56, lead a positive and pro-social life. You were a police officer and you were a founding member of the police dive team.
"You are someone who did many acts which had a positive effect upon your family and the community. I cannot give any further acknowledgement for what has taken place since that time."
"I have to hold you accountable and responsible for the harm you have caused to your victims and I have to provide protection for the community," Judge Crayton said.
"I have to denounce your offending and deter you, but most importantly others who may be tempted to offend in a similar way."
Judge Crayton sentenced Minnell to 14-and-a-half years' imprisonment with a minimum non-parole period of seven years.
