Mariska Hargitay has been investigating crimes as Olivia Benson on Law & Order for almost two decades. And now she’s fighting for real-life justice to end rape-kit backlog, which is the subject of her new HBO documentary, I Am Evidence.

“Being on this show for this many years and living in this material that has been so painful, so prevalent, I felt like, why me?” Hargitay, 54, tells PEOPLE in this week’s cover story, on stands Friday. “I was trying in life to search for the signs, if you will, but why am I here? What am I supposed to do with it? When I learnt about the backlog, it sort of took me a minute to actually download it because you thought: This is America. It can’t be happening. This idea of blowing it up, shining a big beautiful, high voltage light on it was the answer.”

It’s estimated that hundreds of thousands of rape kits — a collection of DNA evidence removed a from a sexual-assault victim through a lengthy and invasive process — go untested in police departments and crime storage lab facilities across the country. This generally occurs because detectives or prosecutors have deemed a victim to be less than “perfect” and do not feel the case merits further investigation.

“The movie has been [made] to provoke outrage, literally,” the Golden Globe-winning actress says. “Each untested kit represents a lost opportunity to bring justice to a survivor of sexual violence, as well as safety to a community.”

As the producer of I Am Evidence, Hargitay spotlights not only the enormity of the problem, but also those who have started working through the backlog. For example in Michigan’s Wayne County, prosecutor Kym Worthy has overseen the testing of 10,000 of Detroit’s 11,341 backlogged kits, resulting in the identification of 817 suspected serial rapists.

“I have been so privileged to witness so many survivors’ stories,” the mom of three says. “I have been first-hand witness to unparalleled courage. We are in this cultural sea-change, pivotal moment that, if it wasn’t accompanied by so much pain, we could focus simply on this silver lining; that the voices we’ve been trying to amplify is finally now.”

The goal now remains for all 50 states to require kits to be counted, tested and acted upon. “Testing rape kits sends a fundamental message to victims: What happened to you matters,” Hargitay asserts. “You matter.”