“FDLE’s subsequent analysis of the information received from Mr. Rivera did not significantly alter our original conclusions,” Bailey wrote in his Nov. 3 letter to Rundle.

Band, a former corruption prosecutor, said it is not uncommon for police investigators and prosecutors to have differing views over how a case should be handled. “There is a natural tension between law enforcement and prosecutors,” he said. “It’s a natural and, to a certain point, healthy part of the system.”

Ready to charge

Miami-Dade prosecutors and FDLE agents first began scrutinizing Rivera in the fall of 2010. At the time, Rivera, a longtime state lawmaker, was campaigning for the congressional seat he won later that year. The investigation was sparked by Herald articles raising questions about Rivera’s income and his financial disclosure reports.

Investigators found that Rivera spent thousands of dollars a month on four different credit cards — and routinely replenished his personal accounts with money from his campaign fund. Agents traced roughly $65,000 from the campaign account that ultimately was used to cover charges on Rivera’s credit cards from 2006 to 2010, the records show.

To the FDLE agents, it appeared Rivera was using campaign donations to subsidize his lifestyle: to pay restaurant tabs, to cover medical bills and to pay for trips with his girlfriend.

The agents also believed that Rivera used campaign funds to pay for expenses that also had been billed to the state, which covers travel and other costs for lawmakers doing legislative work. They estimated that Rivera double-billed the state for more than $25,000 — an accusation Rivera repeatedly denied.

By July 2011, Miami-Dade prosecutors appeared in agreement with the investigators — and appeared ready to bring charges against the congressman.

On July 5, Band called then-prosecutor Joe Centorino offering to provide a box of records from Rivera explaining his campaign spending. “I just suggested that, if he decides to do so, he should do so very soon,” Centorino wrote in a later e-mail to FDLE investigator Lycett.

In the following weeks, Centorino and another prosecutor, Jose Arrojo, began writing up drafts of a criminal complaint against Rivera — mindful that, as more time lapsed, the statute of limitations could bar prosecution on some potential crimes. “The State Attorney expects to see at least a rough but completed arrest warrant sometime by the end of next week,” Arrojo wrote to investigators and fellow prosecutors in an Aug. 5 e-mail.

But the case against Rivera soon began to dissolve.

Accounting mystery

On Aug. 23, Rivera and Band met with Lycett, Centorino and prosecutor Howard Rosen to explain the congressman’s muddy finances, detailed in a 149-page spreadsheet. Though it appeared Rivera used campaign donations to pay off his personal credit cards, Rivera insisted that the monthly campaign checks did not correspond to the monthly credit-card bills. He said he always had a running debt for out-of-pocket campaign costs, allowing Rivera to reimburse himself for past debts.

“When I’m reimbursed, it doesn’t mean reimbursed for that month,” Rivera told investigators, according to notes of the meeting. “I was always in deficit.”