Mystery Man Behind $3.6 Billion in Muni Lawsuits Steps Forward

In 2015, Johan Rosenberg was granted U.S. Patent No. 8,935,181 on an unusual invention: software that he claimed could ferret out Wall Street chicanery.

With the help of MuniPriceTracker, Rosenberg combed through thousands of deals in the vast U.S. municipal-bond market.

Now, after working for years under a cloak of anonymity, Rosenberg has finally stepped forward -- and put his name to some startling allegations. He says 16 banks colluded to set the interest rates artificially high on a certain kind of municipal debt, potentially profiting at taxpayers’ expense.

The claims are all the more remarkable because they’re coming from ...