Each of the three defendants pleaded guilty last month to a fraud conspiracy charge that carries up to 20 years in prison, though Shepherd is expected to receive a shorter sentence because he only had a supporting role.

None of their inmate clients ever provided any useful information or received shorter prison terms during the course of their scheme, which ran from 2009 to 2016.

Defense attorneys for Warrick, the ringleader who owned Private Services, and Bush, his partner, could not be reached for comment. Shepherd’s attorney, Jason Kreiss, said his client was “looking forward to moving on with his life.”

Using aliases such as “Peter Candlewood,” “Diane Lane” and “Diane Rice,” the three defendants conspired to target inmates at the Federal Correctional Institutional in Southwest Miami and other prisons by promising that they could provide services to help them obtain credit for “substantial assistance.” It’s a legal term that comes into play in the federal justice system when convicted felons with insider information on other criminal activity try to curry favor with agents and prosecutors in the hope of reducing their prison time.

As part of the scheme, Warrick and Bush provided fake invoices and fraudulent documents showing agreements benefiting inmates between various U.S. attorney’s offices, including two in New York, and Private Services.

“In fact, the agreements were fake, the prosecutors’ signatures were forged, and no substantial assistance was provided on behalf of these inmates,” according to the U.S. attorney’s office in Miami.

Instead, the three defendants received regular payments from the relatives of federal inmates for their personal use, including spending the money on luxury cars, vacations and gambling activities.