US District Court Judge Richard Stearns said in his decision that he severed the trials of Barry Cadden and Glenn Chin "reluctantly" because their lawyers plan different defenses and because of an imbalance of evidence.
Cadden was the co-founder of the New England Compounding Center in Framingham, while Chin was the now-closed business' supervisory pharmacist. Prosecutors say the company distributed tainted medications.
They are charged in a racketeering indictment with causing the deaths of 25 patients in seven states. Both have pleaded not guilty and are free on bail.