(CBS) — A lawsuit against Northwestern University and a former journalism professor is being allowed to proceed – according to a federal judge’s ruling Tuesday.

The lawsuit was filed by Alstory Simon. He is suing Northwestern, former journalism professor David Protess and a private investigator claiming they framed him for murder. Simon is suing for $40 million.

He was freed from prison a year and a half ago when the state’s attorney threw out double murder charges against him.

It was Northwestern students and Protess and the investigator who were responsible for Simon to be charged and for Anthony Porter to be freed from prison. Simon spent 15 years in prison.

A judge now says Simon’s lawsuit may proceed, that Simon’s claim of malicious prosecution is plausible.

Next step in the case is April 19.