DENVER - A federal judge has ruled that former Denver Broncos linebacker Bill Romanowski could be forced to pay about $5 million in back taxes because of a horse-breeding scheme he says he got caught up in.

The U.S. Tax Court decision found Romanowski, his wife Jill and a business they created in 2003 to invest in a Kentucky-based horse breeder improperly took deductions dating back to 1998.

According to the Denver Post, the deductions were related to more than $13 million the Romanowskis borrowed to invest in a breeding operation called ClassicStar. The company eventually went bankrupt, and its executives were convicted of federal tax fraud.

The Romanowskis said they were brought into the investment scam by Rodney Atherton, a Denver tax attorney who was also at the center of the near-collapse of Colorado's conservation-easement program in 2007, the newspaper reported.

Romanowski and his wife still have the right to appeal the decision.