This is a problem which has been plaguing the country for ages, one which we’ve known about for at least the past two decades, but are only now beginning to make some progress on. We’re speaking of the issue of a mountain of untested rape kits gathering dust in police storage facilities around the nation. In some cases, even more alarmingly, the kits were simply destroyed after waiting in storage for too long.

These kits are the sealed containers of evidence, collected by doctors for the police, from the bodies, clothing or personal effects of women who reported being raped. Most of the women reasonably assumed that the evidence would be examined and tested, hopefully assisting in identifying and apprehending their attackers. But in literally hundreds of thousands of cases, the evidence never saw the light of day again.

Now, years after this problem was exposed, law enforcement in at least some areas has been working through the backlog. This has led to some staggering discoveries, but also very painful decisions as to what to do with the results and whether or not the victims should be informed. Jessica Contrera has a deep dive into the subject at the WaPo this week and it turns out to be an even more painful topic that many of us probably imagined.

In New York City, an estimated 17,000 kits went untested. In Houston, there were 6,000. In Detroit, Los Angeles and Memphis, there were more than 11,000 each. Over the past two decades, the “rape kit backlog” has been in the news so many times that now, slowly, the problem is being fixed across the country. Under pressure from activists and legislators, states and cities big and small are counting their kits and sending them to be tested. And then, they are beginning to quietly struggle with a far more complicated challenge: What happens once the kits come back?

The experiences of other cities offered no obvious answer. “I didn’t see them wrestle with any issue as deeply, with as much worry and compassion, as this one,” says Rebecca Campbell, a researcher who spent three years observing the handling of Detroit’s untested kits. “This one brought them to their knees.” In Detroit, it was ultimately decided that, at least at first, victims would be notified only if their kits resulted in a “hit,” meaning the DNA found in the box matched a person in the Combined DNA Index System, a national database of offenders better known as CODIS.

Houston tried a different model. A hotline was set up and publicized, so that any victim who wanted information about their old kit could ask for it. Then, police and prosecutors combed through the CODIS hits and decided which cases actually had a chance of moving forward in the criminal justice system. Victims were notified only if their cases seemed “actionable.” “What’s at stake is the well-being and mental health of sexual assault victims,” says Noël Busch-Armendariz, a researcher who was involved in Houston’s process. “You never know where people are in their lives and what support systems they have or don’t have ready for them.”

The numbers in that article are alarming but they don’t tell the whole story. This past December, Newsweek covered an analysis done of forensic evidence recovered in the greater Detroit area. The Motor City was sitting on more than 11,000 untested kits which they slowly processed over a period of years. After the test results were compiled, they discovered that there were more than 800 serial rapists who had gone undetected in that region.

According to the nonprofit organization End the Backlog, there are literally hundreds of thousands of kits awaiting testing across the country. Newsweek reports that the White House estimated the number to be in the area of 400,000 in 2015. Based on the findings in Detroit, that means that there are very likely as many as 30,000 repeat rapists out there across America who have not been detected yet, but could be identified if all the kits were finally tested.

Two obvious responses are each problematic. First, it’s easy to raise an uproar and demand to know why every kit wasn’t tested to begin with and demand that heads roll in the law enforcement community. Unfortunately, the reality is more complicated. Processing the kits is expensive and time-consuming. Laws differ from state to state or even city to city as to how quickly the evidence must be tested or if it’s even mandatory to test them at all. Officials working under strained budgets have to make some tough calls. One idea on this front is to see if federal law enforcement funding could be found to allow state and local police to begin getting every kit tested in a prompt fashion.

The second question is tougher. What do we do with the information obtained when these cold case kits are finally tested? If it’s a fairly recent case and you get a hit in CODIS (the Combined DNA Index System) perhaps you’ll obtain a conviction. But what about the older kits? What do you say to a woman who went through the examination ten years ago and the statute of limitations has expired? Sorry doesn’t seem to cover it.

This will be expensive and time consuming but it still sounds like a job which has to be finished. More to the point, however, is the need to ensure that new cases have evidence processed and tested in a timely fashion so the problem doesn’t continue to fester for decades longer.