Lawyer Andreas Grabenweger said his client will appeal the ruling.
Prosecutors said the woman, identified only as Heidemarie S., allegedly sent more than 100 letters to the American actor in pursuit of an autograph and then sent a death threat in 2007 when he refused to give her one.
A court-appointed psychiatrist testified earlier that the woman has a "profound personality disorder."
The woman, who is in her early 40s, twice failed to show up for her trial and was taken into custody last month after she was arrested in Mexico on immigration charges and deported back to Austria.
Caruso plays Miami police Lt. Horatio Caine in the CBS television network crime drama.
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