At least 400,000 rape kits containing critical DNA that could help convict a criminal are sitting untested in labs around the country. Victims who submitted evidence assumed the police were searching for their attackers using the kits, but hundreds of thousands were never processed.

A new federal law aims to reduce this enormous backlog of untested kits, but time is running out in some cases.

CNN's Randi Kaye met one woman who followed up on her case decades later and was horrified to discover her rape kit was untested. When police finally processed the evidence, it was just a matter of months before they found the man who brutally raped Carol Bart in1984. But it was too late for her to press charges against Joseph Houston and seek justice because of the statute of limitations in Texas.

Lavinia Masters's case had gone cold too. She was attacked in 1985 at age 13. After 21 years, the kit was unearthed and tested and the rapist was found. Too many years had passed for Lavinia to bring charges, but the DNA match in her case helped influence the decision to deny him parole. He was already serving time for raping two other women.

Dallas Police Sergeant Patrick Welsh started a sexual assault cold case program when he discovered the rape kit backlog. He asked the Southwestern Institute of Forensic Sciences to test thousands of kits dating back to 1970. The initiative has helped them solve at least 80 cases from the early '80s and '90s.