That’s what’s striking about ViCAP today: the paucity of information it contains. Only about 1,400 police agencies in the U.S., out of roughly 18,000, participate in the system. The database receives reports from far less than 1 percent of the violent crimes committed annually. It’s not even clear how many crimes the database has helped solve. The FBI does not release any figures. A review in the 1990s found it had linked only 33 crimes in 12 years.

Canadian authorities built on the original ViCAP framework to develop a modern and sophisticated system capable of identifying patterns and linking crimes. It has proven particularly successful at analyzing sexual-assault cases. But three decades and an estimated $30 million later, the FBI’s system remains stuck in the past, the John Henry of data mining. ViCAP was supposed to revolutionize American law enforcement. That revolution never came.

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Few law-enforcement officials dispute the potential of a system like ViCAP to help solve crimes. But the FBI has never delivered on its promise. In an agency with an $8.2 billion yearly budget, ViCAP receives around $800,000 a year to keep the system going. The ViCAP program has a staff of 12. Travel and training have been cut back in recent years. Last year, the program provided analytical assistance to local cops just 220 times. As a result, the program has done little to close the gap that prompted Congress to create it. Police agencies still don’t talk to each other on many occasions. Killers and rapists continue to escape arrest by exploiting that weakness. “The need is vital,” said Ritchie Martinez, the former president of the International Association of Law Enforcement Intelligence Analysts. “But ViCAP is not filling it.”

Local cops say the system is confusing and cumbersome. Entering a single case into the database can take an hour and hits—where an unsolved crime is connected to a prior incident—are rare. False positives are common. Many also said the FBI does little to teach cops how to use the system. Training has dropped from a high of about 5,500 officers in 2012 to 1,200 last year.

“We don’t really use ViCAP,” said Jeff Jensen, a criminal analyst for the Phoenix police department with 15 years of experience. “It really is quite a chore.”

The FBI has contributed to the confusion by misrepresenting the system. On its website, the FBI says cases in its database are “continually compared” for matches as new cases are entered. But in an interview, program officials said that does not happen. “We have plans for that in the future,” said Nathan Graham, a crime analyst for the program. The agency said it would update the information on its website.

The agency’s indifference to the database is particularly noteworthy at a time when emerging research suggests that such a tool could be especially useful in rape investigations.