Despite a quick start and rapid revelations over the cause of the crash, it has been harder pinning down who can be held criminally responsible, with the question of doctor-patient confidentiality at the heart of the case.
Hardly an hour and a half after the plane crashed into the French Alps on March 24, 2105, Marseille prosecutor Brice Robin overflew the site. The plane was shattered into such small pieces that they were difficult to discern from the air.
But the black box voice and flight recorders were quickly recovered virtually intact and it was swiftly revealed that 27-year-old co-pilot Andreas Lubitz deliberately crashed the plane, killing all 144 passengers and six crew, mostly from Spain and Germany.
Although Lubitz cannot be brought to justice for murder, Germanwings, a low-cost subsidiary of Frankfurt-based Lufthansa, could bear some responsibility for the disaster.
Three months after the crash, a three-judge panel in Marseille launched an investigation against unknown persons for manslaughter.
A central issue is that of reconciling doctor-patient confidentiality with
the responsibility of an airline for the lives of its passengers.
French prosecutors said Lubitz, who suffered from psychosis, was terrified of losing his sight and consulted 41 different doctors in the previous five years, including psychiatrists as well as ear, throat and nose specialists.
German prosecutors said a search of Lubitz's flat had found medical
documents, including a torn-up sick leave note from the day of the crash, which supported "the assumption that the deceased had concealed his illness from his employer."
The Marseille probe is complicated by the fact that German rules governing companies' responsibilities are different, as is the treatment of the violation of doctor-patient responsibility.
The French investigators called earlier this month for "clearer rules" on
the lifting of medical confidentiality if pilots show signs of psychological
In their final conclusions on the disaster, French civil aviation experts
recommended more stringent medical checks for pilots, but stopped short of suggesting changes to the current system of flight deck door locks, which can only be opened by the pilot in the cockpit.
German investigators are conducting a parallel probe, but are still bogged down in translation and evaluation of French prosecutors' documents, and said in March a "conclusion is not expected anytime soon."
Meanwhile impatient relatives are planning to sue the airline's parent company Lufthansa in the United States, claiming that Lubitz should never have been allowed to fly a plane.
"The only thing that interests me is that we find whoever... failed to prevent Lubitz from flying a plane," said Annette Bless, whose daughter Elena died in the tragedy, a day before she would have turned 16.