Wichita ? A Kansas doctor accused of illegally prescribing drugs linked to 68 deaths testified that he knew some patients had died from overdoses, but he said his clinic changed its practices to prevent future overdoses.

Dr. Stephen Schneider and his wife, Linda, were charged in a 34-count indictment with illegally prescribing drugs and committing health care fraud and money laundering. Schneider testified in his own defense Wednesday and returned to the stand Thursday to undergo cross examination by a federal prosecutor.

When Assistant U.S. Attorney Tanya Treadway asked Schneider whether he knew that people who received prescriptions from him had died, he said, “I know of some.”

Schneider testified earlier that his practice evolved in an effort to prevent overdoses. The clinic changed its pain management agreement several times.

Treadway also tried to cast doubt on the doctor’s claim during his testimony that the reason his clinic was overwhelmed with 10,000 patients was because it was one of the few in the area that accepted lower-paying Medicaid patients. But Treadway pointed out Thursday that 320 other providers in the area took Medicaid patients.