Culpability

Question: Consider the culpability of a doctor in a HIV/patient confidentiality case. A couple went to a doctor together to be tested for aids. The doctor gave individual reports to each patient, but didn't share the report results with the other member of the couple. The aids result was positive for the guy. The guy lied to his prospective spouse and claimed that his results were negative. The marriage proceeded and the woman was then infected. Is the doctor culpable?
Which is more important - patient confidentiality or duty of care? Under what circumstances can a doctor breach confidentiality?
Is it right to sue a well-financed doctor because he could have acted, instead of taking action against a person who has deliberately and maliciously concealed life threatening information?