HOUSTON--A doctor has pleaded guilty to fraudulently billing Medicare for millions by selling certificates of medical necessity and prescriptions for power chairs and other DME.

Dr. Callie Hall Herpin admitted she participated in a conspiracy that resulted in fraudulent billings to Medicare of $30 million, as well as a money laundering count, according to the U.S. Attorney's Office for the Southern District of Texas.

According to a statement issued by the U.S. Attorney's Office:

Herpin said at a hearing last week that she and co-defendant Etta Mae Williams sold CMNs to providers for approximately $200, writing no less than 920 fraudulent orders and receiving at least $184,000 in return. The Texas doctor also admitted she did not examine all of the patients to determine their eligibility for the power chairs, adding that in many instances providers brought copies of the Medicare beneficiaries' driver's licenses and Medicare cards to the two defendants, who used the information to produce the fraudulent CMNs.

Herpin also stated that she and Williams sold prescriptions for controlled substances--specifically hydrocodone products and codeine cough syrup. The two wrote at least 17,086 prescriptions, receiving at least $1.7 million, she admitted.

Williams faces a maximum of 20 years in prison and a $500,000 fine on the money laundering count. Both defendants face a maximum sentence of five years in prison and fines of $250,000 on each of the two conspiracy counts.