Published: Jan 14, 2014 4:05 PM EST
Updated: Jan 14, 2014 6:12 PM EST

LEE COUNTY, Fla.- Jurors heard testimony from two of Andrew Castor's former roommates, in his murder trial today.

They say Castor seemed depressed and detached on August 2, 2008, when Cape Coral Police say he stabbed Bianca Interiano to death in her apartment on Country Club Boulevard.

Castor's lawyers are trying to prove he was insane at the time.

He faces life in prison, if convicted.