Paul Callan is a CNN legal analyst, a former New York homicide prosecutor and current counsel at the New York law firm of Edelman & Edelman PC, focusing on wrongful conviction and civil rights cases. Follow him on Twitter @paulcallan. The opinions expressed in this commentary are his own.

(CNN) The search warrant raid on the office, home and hotel room of Michael Cohen, the personal counsel to the President, is an extraordinarily unusual and highly aggressive move by federal prosecutors. It sends a strong message that Special Counsel Robert Mueller's investigation has uncovered a lead suggesting criminality related to Cohen's law office probably unrelated to Mueller's Russia election meddling probe.

Mueller has now developed evidence sufficient to persuade a federal judge that there is "probable cause" to believe that Cohen has in his possession evidence of a crime. Most experienced criminal lawyers would likely suspect that the Stormy Daniels $130,000 "hush money" payoff is the primary clue that sparked a closer look at Cohen's law office.

Everything about the payment looks unusual, from Cohen's claim that he used a personal line of credit on his house to fund the payment to statements by both Cohen and the President that Mr. Trump knew nothing about the payment. Lawyers don't customarily fund the contractual obligations of their clients as such actions can, depending on the circumstances, constitute unethical conduct by the attorney fronting or "gifting" the funds.

In addition, the timing of the $130,000 payment so close to the presidential election may suggest an unreported and illegal campaign contribution. How the money is treated for tax purposes may also trigger other legal concerns. Payments to people who claim to have had affairs with public figures are not currently tax deductible under the IRS Code even if your primary residences are Trump Tower and the White House.

The search warrants may uncover evidence of prior payoffs and the feds will have a strong interest in where the money came from and whether it was deducted as a Trump or Cohen business expense. Of course the search may also exonerate both men of any criminal conduct.

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