Content note: This article contains a graphic description of sexual assault.

Sexual assault in the military could be twice as common as the Pentagon claims, according to a report released this week by the office of Sen. Kirsten Gillibrand (D-NY).

In a review of 107 case files on sexual assault from the nation’s largest military bases, 53 percent of the alleged victims were civilians—either the spouses of military service members, or women who lived near a military base.

The “alarming rates” of assault against these two groups of civilian victims aren’t included in the Department of Defense’s annual surveys on the prevalence of sexual assault, Gillibrand said in a statement.

“The more we learn, the worse the problem gets,” said Gillibrand, who has led the congressional charge to change the Pentagon’s sexual assault policies.

The Pentagon estimates that 20,000 service members were victims of sexual assault in 2014, but the total number of people assaulted by members of the military might be as high as 42,000. These uncounted victims are “part of the overall military community, yet remain in the shadows,” the report says.

It’s not clear whether the 53 percent figure holds true for the military as a whole. It’s possible, for instance, that sexual assaults against civilians are more prevalent or better reported at the four major bases surveyed in the study.

The report notes that the 107 case files reviewed are “redacted, incomplete, and often do not contain all relevant data pertaining to the cases.”

But that incompleteness is another symptom of the problem, the report charges. It “calls into question the [Defense] Department’s commitment to transparency.”

Gillibrand’s office asked for all relevant cases from the past five years; instead, they got reports from one year. The number of reports was also suspiciously low given other data about the prevalence of assaults.

And the actual outcomes of these cases “suggests a large scale systemic failure and a culture that protects the accused and ostracizes the survivor at the expense of the public and the servicemembers’ safety,” the report reads.

Most military spouses declined to press charges, and none of those cases reviewed that went forward resulted in a conviction.

Almost half of all survivors gave up after taking the first steps through the process, which the report says could indicate a lack of faith in the system or problems with retaliation.

Twenty-four of the 107 cases proceeded to trial. Eleven of those resulted in a sexual assault conviction, six resulted in conviction on a lesser charge, and seven resulted in acquittals.

The report also looked behind the numbers, highlighting several case studies that show how “dysfunctional” the current military justice system is.

Serial rapists may have been allowed to walk free in two cases. In one case, the suspect was discharged despite a recommendation that he be court-martialed; in the other, there was no record of an investigation or punishment, despite DNA evidence.

A 34-year-old Marine allegedly gave wine to a 17-year-old civilian and raped her, held her down, and inserted an object into her anus, but he received no trial; instead he paid a fine and was demoted one rank after pleading guilty to adultery and giving alcohol to a minor.

A military wife committed suicide after alleging rape by her husband, who wasn’t charged despite physical evidence of assault, including dried blood and bruising.

These findings point to the need for independent prosecutors, not military commanders, to adjudicate sexual assault cases, the report says.

Gillibrand has been a vocal advocate for this policy change, citing the lack of legal training and frequent conflicts of interest among commanders.

The Pentagon has resisted the reforms in Gillibrand’s Military Justice Improvement Act, despite growing calls from advocates who say that true reform isn’t possible without putting independent prosecutors, not military commanders, in charge of the adjudication process. Gillibrand has gotten a bipartisan majority of senators to sign on to her proposal, but so far it hasn’t been enough to defeat a filibuster.