An analyst works on a piece of evidence at the South Dakota Forensic Laboratory, left. An examination room at the laboratory, right. Photos: Courtesy of South Dakota Forensic Laboratory

Testing the backlog of untested rape kits stored in evidence rooms and on crime lab shelves nationwide has been a major initiative costing billions, and involving evidence taken from thousands of victims over decades.

Some cities and states are making the push to test the evidence, and see if it can solve old cases – and potentially prevent new ones.

South Dakota is the latest success story. The state announced earlier this month they have eliminated their rape kit backlog of 504 untested kits from years past.

The kits had been collected from two of the largest law enforcement agencies in South Dakota.

About half – 254 kits – yielded enough biological evidence for DNA testing, said Sara Rabern, a spokeswoman for the state attorney general’s office.

Sixteen percent – or 83 of the kits – yielded hits in CODIS, the national DNA database, she added.

Disposition of those DNA samples – and whether they mean further prosecutions of cases old and new – is not yet clear.

“A rape victim who has the courage to report a sexual crime deserves to have all the potential evidence tested,” said Marty Jackley, the South Dakota attorney general, as part of the announcement. “The state forensic lab and our local enforcement partners should be commended for completing this additional workload efficiently and accurately.”

The South Dakota Forensic Laboratory had hired an additional DNA analyst, which allowed the major push through the backlog in 2016. The lab completed 644 biology assignments on 396 cases to work through the pile of cases last year alone. The additional analyst, and additional hours put into completing the backlog, were paid from the state budget – and without federal funding.

The state also passed a law last year requiring the testing of all rape kits heading forward.

Other cities and states that have worked through their backlog have discovered perpetrators who were already in CODIS.

Houston successfully worked through 6,600 stockpiled kits and found 850 DNA hits – a rate of roughly 12 percent, they announced in 2015.

Colorado worked through its backlog of 3,542 kits, the state Bureau of Investigation announced last summer. About half yielded DNA profiles, they said. A total of 691 of the profiles “generated investigative leads” for law enforcement through CODIS hits, according to The Denver Post. That rate is roughly 20 percent of the total kits.

According to the Joyful Heart Foundation, an anti-rape group, seven states have counted up a stockpile of more than 24,000 untested kits. Arizona alone has more than 6,000 that are still awaiting analysis.

Some of the investigative breakthroughs are reached a crucial chronological point. Some key states have statutes of limitation on sexual assault and other crimes which are running out as the kits remain untested, according to a Forensic Magazine analysis compiled in October 2015