“Law & Order: Special Victims Unit” star Mariska Hargitay is helping victims of rape off-screen, too. Hargitay was spotted at restaurant Sienna in East Hampton saying she’s campaigning for law-enforcement agencies to deal with a national backlog of untested “rape kits.” “There are hundreds of thousands of untested rape kits in police and crime- lab storage facilities,” she wrote in a recent column online. “Every year, thousands of individuals take the courageous step of reporting their rape to the police . . . The evidence is then collected in a ‘Sexual Assault Evidence Collection Kit’ — a rape kit . . . And yet, hundreds of thousands of times, a decision is made not to process the evidence. Too difficult to prosecute, too murky, too expensive — not a priority.” A source said Hargitay will shoot a documentary on this subject in two months. She has a producer for the project and is meeting with directors. The actress was overheard further explaining, “When you don’t test a rape kit, it sends the message that’s it’s not a serious crime, and I’m beyond outraged.”