Christopher Simcox, a founder of the now-disbanded Minuteman border patrol group, has been sentenced in Arizona to more than 19 years in prison for sexual abuse of a 5-year-old girl, in a case that drew the attention of the Supreme Court after Mr. Simcox tried to question the young victim.

Mr. Simcox, 55, was found guilty last month of molesting the girl, who was a friend of his 6-year-old daughter, in 2012 and 2013 during scheduled parental visits at his apartment after he and his wife divorced.

The 5-year-old girl told her mother of the abuse, who called law enforcement.

In a statement on Monday, the Maricopa County attorney, Bill Montgomery, said the 19-and-a-half-year sentence involved two counts of molestation of a child and one count of furnishing obscene materials to a minor.

“The defendant committed unconscionable acts against a young child, the emotional and psychological effects of which she’ll have to deal with her entire life,” Mr. Montgomery said. He added that the sentence “won’t take back the harm he has done, but it removes the opportunity for him to prey on another child.”