The three are also accused of breaking into two government sites and blocking public access for days.
The names, phone numbers, and personal and professional email addresses of 541 police officers who were members of the SGP-FO police union were posted online in January 2012 after a hacking attack claimed by the Anonymous organization, a loosely-associated international network of hackers.
The police officers are asking for 73,000 euros in damages overall, another lawyer for one of the defendants, Matthieu Hy, said.
The criminal court will deliver its ruling March 22.
Merchat told France Info radio "the contact information for these police officers is accessible to all people planning to target France".
After his arrest, one of the defendants told the police the hacking attack was carried out in retaliation to the arrests of several Anonymous activists by French police and the closure of the popular website Megaupload by the US department of justice days earlier.
The shutdown of Megaupload, a platform that ran online storage and viewing services, led to so-called denial-of-service (DoS) attacks on a range of government, police and copyright organization websites by the Anonymous group, including the French attacks, according to court documents.