The family of a girl who authorities say suffered years of sexual abuse by a relative is taking the unusual step of waging a legal fight against a Virginia prosecutor to try to win a longer sentence for the defendant.

The family, which has retained an attorney, hopes to persuade a Fairfax County Circuit Court judge to reject a plea deal at a sentencing hearing for Oscar Zaldivar, 53, on Friday. The plea deal caps Zaldivar’s sentence at a maximum of a little more than 17 years.

But the girl’s parents said in an interview that Zaldivar, who has already entered a guilty plea, deserves decades more in prison.

Prosecutors have said in court that Zaldivar molested the girl over a period of seven years, including a years-long stretch when the abuse occurred at least once a week while the girl was in grade school. In addition, they point out Zaldivar molested a second girl who was not a relative.

The girl’s parents said they think the office of Commonwealth’s Attorney Steve T. Descano has ignored their wishes and has not offered an explanation of the rationale used to arrive at the proposed sentence. They have filed a motion objecting to the plea deal.

“They put more importance on the defendants than on the victims,” the girl’s father said of Descano’s office. “They leave the victims on the side. That’s the way we feel.”

The Washington Post does not generally identify the victims of sexual assault and is not naming the girl’s parents, describing the girl’s exact relation to Zaldivar or publishing some details of the crimes to avoid indirectly identifying her.

Descano’s spokesman, Ben Shnider, said in a statement that the crimes in this case are “horrific and a priority for our office” and that the proposed sentence was tougher than most handed out for similar offenses in Virginia.

“We value and respect the perspective of the family and we were in touch with them throughout the plea negotiations so that we could take that perspective into account,” Shnider said.

Victims sometimes oppose sentences sought by prosecutors, but it’s exceedingly rare for them to take legal action to try to alter the outcome.

Descano is one of a wave of liberal prosecutors who have won election in recent years across the nation, promising to take a less punitive approach and to undo historical inequities in the justice system.

While some victims have applauded the approach, others said they have felt abandoned by liberal prosecutors. In Los Angeles, a handful of crime victims has been part of an effort to recall District Attorney George Gascón. Others in San Francisco have complained loudly about liberal prosecutor Chesa Boudin.

Supporters of two recall campaigns targeting Descano and other liberal prosecutors in Northern Virginia argue he has been insufficiently tough on crime to the detriment of some victims. The family members in the Zaldivar case said they have no connections to those efforts.

A Fairfax County grand jury indicted Zaldivar in 2019 on three counts of aggravated sexual battery and two counts of sodomy in connection with the abuse of the girl who is a relative. He was indicted on abduction with intent to defile and one count of sexual battery in the case of the girl who is not a relative.

Under Virginia law, the sodomy counts alone carry a mandatory sentence of life in prison, since the acts involved an adult and a child under 13. The other counts carry maximum sentences that add up to more than 80 years.

The case began under Fairfax County’s previous prosecutor, Raymond F. Morrogh, who the family said initially offered Zaldivar a plea deal that would remove the language in the indictments requiring mandatory life terms and cap his sentence at a maximum of 30 years.

The girl’s family said it wasn’t pleased with the offer; Zaldivar ultimately rejected it and the case proceeded toward trial. Descano beat Morrogh in the 2019 Democratic primary and took office last year after winning the general election.

The parents said they met in April with assistant prosecutor Nathan D. Freier, who told them Descano’s office had worked out a proposed plea deal with Zaldivar that called for a maximum sentence of 19 years. That was ultimately reduced to 17 years and two months.

Paul Mickelsen, an attorney for the parents who attended the meeting, said Freier asked them how they felt about the deal and the family told the prosecutor it was a miscarriage of justice.

Mickelsen said Freier indicated he wasn’t satisfied with the proposed plea deal but feared challenging it because he might lose his job.

Mickelsen said he also asked Freier about the reasoning behind the deal and that Freier said “no reasoning has been given” from his superiors. Family members said they were dismayed and hurt that they couldn’t get that basic information.

Freier referred all questions about the interaction to Shnider. The spokesman said in his statement only that Freier “does not disagree with this plea agreement.”

Under the terms of the plea deal, Zaldivar entered at a May hearing what are known as Alford pleas to the five counts in the case involving the relative and one count of sexual battery in the case involving the nonrelative.

In Alford pleas, a defendant does not admit guilt but acknowledges prosecutors have enough evidence to obtain a conviction. Freier said at the hearing that the sexual abuse began when the relative of Zaldivar was 5 or 6 years old and stretched on for years.

The prosecutor said the victim told investigators that Zaldivar would lock her in a room to abuse her with other family members in the house. The girl told investigators Zaldivar told her to keep the molestation a secret from her parents and others.

Freier graphically described one encounter, where the girl resisted and screamed for help. He said Zaldivar admitted to molesting both girls when he was interviewed by police. The girl’s family said she was ready to testify against Zaldivar at a trial.

Shnider said in his statement that Descano’s office willingly struck the mandatory life sentence language on the sodomy charges because the office has a policy of avoiding mandatory minimums whenever possible. Shnider said mandatory sentences play a “pernicious role” in the justice system and don’t allow stakeholders to make individualized case determinations.

The spokesman said the proposed 17-year sentence is higher than 75 percent of sentences for similar offenses handed out in Virginia as determined by the sentencing guidelines that judges use to help fix penalties in the state. The guidelines rely on decades of sentencing data.

Shnider pointed to a similar case this month in Nelson County, Va., in which a jury gave the defendant a 17-year sentence.

But the parents of the victim argue that Zaldivar’s case is especially terrible. They point to the nature of the abuse, its frequency and that it continued over years.

The parents said the crimes have devastated their family. Their daughter has suffered depression. They say most relatives have turned their backs on them because Zaldivar has told them he didn’t commit the crimes.

The Fairfax County public defenders representing Zaldivar argued in a motion responding to the family’s filing that the parents have no legal authority to object to the plea agreement under Virginia law, a position that is shared by Descano’s office.

Fairfax County public defender Bryan Kennedy said in a statement that Zaldivar has no prior criminal record and spent years gainfully employed.

“The main driver of mass incarceration in this country has been extreme sentences for violent crimes,” Kennedy said. “People convicted of sexual and violent offenses have the lowest rates of recidivism among all types of offenses. The criminal legal system must look past retribution and consider the actual utility of additional incarceration.”

At the sentencing hearing Friday, Circuit Court Judge Thomas P. Mann could choose to accept the plea deal with the 17-year sentence, lower the penalty or reject the plea deal altogether. If the last happened, Zaldivar could withdraw his guilty pleas and the case would continue.

The girl’s parents said they and their daughter want to testify at Friday’s hearing to make their feelings known about the proposed sentence. It’s unclear whether Freier will call them to take the stand.

“Sometimes I think if this happened to a close friend I’d think twice about advising them to get involved in this process,” the mother of the girl said in Spanish through an interpreter. “It hurts more to see that justice is not done.”