A joint trial of ex-pharmaceutical executive Martin Shkreli and Evan Greebel, his co-defendant in a fraud case and his former lawyer, would present a “serious risk” that Shkreli would not receive a fair trial, a federal judge ruled on Wednesday.

Shkreli, the founder and former CEO of Turing Pharmaceuticals, and Greebel, a former partner with Katten Muchin Rosenman, are accused of working together in a scheme to defraud investors in Retrophin Inc. to pay off investors in two hedge funds that Shkreli also founded, MSMB Capital Management and MSMB Healthcare.

The two defendants, each arrested and charged in 2015, moved to sever their trials, arguing that their defenses would be “mutually antagonistic” and force them to clash with each other while defending themselves against government lawyers.