mike halgren has the latest on the investigation into unnecessary medical procedures. >> reporter: st. joseph medical center will pay 22 million to the feds because of kick backs in exchange for patient referrals but that settlement is notable for what it does not include and that's a deal to stop any criminal prosecution. law professor. >> i'm going to make sure if i give you that amount of money i want you to guarantee me that you're not going to prosecute me criminally. no, we're not going to promise you that. >> reporter: this is what the u.s. attorney told wjz about the possibility of criminal charges. >> the only issue here is -- there's no promise behind that. >> reporter: the settlement also claims st. joseph billed the government or stents. >> reporter: dr. midday strongly denies any wrongdoing. he filed his own lawsuit against st. joseph. three physicians were whistle blowers. >> they are certainly ready to develop rate with the government on whatever next steps the government wants to take but that's up to the government. >> reporter: no one has been charged as a result of