Attorney Jeffrey Denner set up an insanity defense by telling the jury during opening statements that the defendant, whose real name is Christian Karl Gerhartsreiter, suffered from two mental illnesses and didn't know it was wrong to snatch his 7-year-old daughter off the streets of Boston during a supervised visit last July.
Gerhartsreiter was "pushed over the edge" when he lost custody of his daughter in 2007, Denner said.
"He believed that on a moral level ... he had to do this to save his daughter," Denner said.
Gerhartsreiter is accused of shoving a social worker to the ground during the supervised visit, then hustling his daughter into a waiting car and fleeing. They were both found in Baltimore six days later, the girl unharmed.
Prosecutors opened the trial by portraying Gerhartsreiter as a con man who thinks the rules do not apply to him. They allege that he spent months meticulously planning the kidnapping.
Prosecutor David Deakin described how Gerhartsreiter romanced he ex-wife and "dazzled" her with "his personality, his charisma, his likability," but remained vague about his past.
His ex-wife, Sandra Boss, was not in court Thursday, but her father, William Boss, did attend openings.
Authorities say Gerhartsreiter is a German man who has used multiple aliases to work his way into wealthy circles since moving to the U.S. in 1978.