What really happens when a tax case goes criminal? In this episode of the Tax Rep Network Podcast, host Eric Green sits down with former federal prosecutor John Mulcahy—now in private practice at Nixon Peabody—to pull back the curtain on how criminal tax cases are built, reviewed, and prosecuted.

Drawing on over a decade of experience at the U.S. Attorney’s Office and the DOJ’s tax division, John walks through the lifecycle of a criminal tax case—from initial IRS investigation to DOJ review, grand jury proceedings, and ultimately, prosecution decisions. Along the way, he explains why the DOJ still plays a critical gatekeeping role and how consistency in tax enforcement is maintained nationwide.

But this conversation goes beyond process. Eric and John dig into the real-world dynamics that shape outcomes: the discretion of Assistant U.S. Attorneys, the strategic decisions behind charging (or declining) a case, and the often misunderstood role of “willfulness” in tax crimes. Through candid stories and behind-the-scenes insights, they highlight how cases can turn on a single issue—especially intent—and why listening closely to clients can make or break a defense. Now on the defense side, John also shares what it’s like transitioning from prosecutor to advocate—working with clients in crisis, navigating complex facts, and seeing firsthand that every case has more than one side.

If you’re a tax professional, attorney, or anyone curious about how criminal tax enforcement really works, this episode offers a rare insider perspective you won’t hear anywhere else.

Want to contact John?  Email him at: [email protected]