Federal prosecutors say a Miramar attorney overbilled the Seminole Tribe of Florida more than $1 million by inflating invoices and billing for trips never taken and conferences never attended.

Frank Excel Marley III of the Excel Law Firm is expected to make his first appearance before a federal magistrate Tuesday.

Also charged in the indictment filed Thursday was his administrative assistant Maria Hussun, who is accused of siphoning off more than $308,000 from the firm’s bank account and depositing nearly half of it in her personal account.

They could face up to 20 years in prison if convicted of one count of wire and mail fraud conspiracy and nine counts of theft from Indian tribal organizations.

There was no answer at Marley’s law firm Friday.

The indictment charges Marley inflated bills submitted by third parties, including outside law firms, and padding expenses from 2006 to 2011. Marley was hired to represent the tribe’s Seminole Sports Management LLC and establish radio stations on the Brighton and Big Cypress reservations

Marley instructed Hussun to "increase the charges invoiced to the tribe by inflating the amount of his (Marley’s) billable hours and billing the tribe for travel, conferences, phone calls and meetings that did not occur," Assistant U.S. Attorney Neil Karabil wrote in the indictment.

Seminole spokesman Gary Bitner referred a call for comment to the U.S. attorney’s office "since this is an active criminal case."

In one instance, the Washington law firm Garvey Shubert & Barer billed Marley in 2007 for $18,146, and he charged the tribe $210,450 for the firm’s work, according to the indictment.

Other law firms whose bills were allegedly inflated were Sheppard Mullin Richter & Hampton of Washington and Wessels & Pautsch of Indianapolis.

Sheppard Mullin submitted a bill of $24,622 in 2007 for the radio project, but Karadbil said Marley billed the tribe $90,000 for the law firm’s work.

Wessels & Pautsch represented Seminole Sports Management in a federal civil action in Wisconsin against a pool cue manufacturer. The firm submitted an invoice to Marley for $89,642 that Karadbil said Marley turned into a $227,925 bill for the tribe.

The indictment alleges Marley changed $29,087 in bills from RF Engineers Inc. for work on the radio stations to $123,000 in bills submitted to the tribe.

The indictment alleges Marley got more blatant in his scheme as time went on. In 2010, he billed the tribe nearly $100,000 to attend nine Native American Broadband Association conferences in Washington that never took place, according to the indictment.

He also billed the tribe $59,000 for the purchase of translators never bought and $19,260 for trips to St. Petersburg and Sarasota never taken, prosecutors allege.