dr giorgi-guarnieri testified on friday during court hearings in washington , d.c. , that will ultimately determine whether and under which conditions john hinckley jr. will be allowed to live full time outside a mental hospital .
one of hinckley 's interests is music , and he sings and plays the guitar that he can spend 17 days a month away from a mental home where he has been for the last three decades at his mother 's virginia home .
hinckley 's lawyers said mental illness drove the then 25-year-old hinckley to shoot the president in 1981 in an effort to impress actress jodie foster .