On 19 July 2011, the Appeals Chamber of the ICTY upheld the first instance decision to convict Hartmann of contempt of court for the section of text called "Vital genocide documents concealed" in her book, Paix et Châtiment, les guerres secrètes de la politique et de la justice internationales, which included the "legal reasoning" of two confidential appellate rulings of the UN Tribunal approving black-outs and exclusions from critical historical war documents showing Serbia's involvement in the Bosnian war of the 1990s.

In July 2015, she issued a book that reveals the role of the west in the runup to Srebrenica's fall, The Srebrenica Affair: The Blood of Realpolitik,[7][8] She was the first journalist to discover in October 1992 the existence and location of a mass grave at Ovčara (Croatia) containing the remains of 263 people who were taken from Vukovar's hospital to a nearby farm and killed on 20 November 1991 by Serb forces.

On 25 May 2006, she gave evidence before the ICTY in the "Vukovar massacre case" against three Yugoslav People's Army (JNA) officers -- Mile Mrkšić, Miroslav Radić and Veselin Šljivančanin—who had been indicted in relation to the Ovčara incident.

[10] On 27 August 2008, Hartmann was indicted by the Tribunal for disclosing, in her book, Paix et châtiment, Les guerres secrètes de la politique et de la justice internationales, confidential information pertaining to two decisions of the Tribunal approving blackouts and exclusions from critical historical war documents provided by Belgrade for the trial of the former Serbian President Slobodan Milošević and showing Serbia's involvement in the Srebrenica massacre.

[11] Hartmann posited that the ICTY Appeals Chamber had used invalid legal reasoning to effectively censor evidence which might have implicated Serbia-Montenegro in the alleged commission of genocide in Bosnia and Herzegovina during the 1990s Balkans wars.

She argued that the war documents censored by the ICTY should have been made available during a separate trial at the International Court of Justice (ICJ) in which Bosnia unsuccessfully tried to sue Serbia for genocide, because they could not prove a direct link between Belgrade and war crimes committed in Bosnia – most notably the massacre of up to 8,000 Bosniak men and boys around Srebrenica in 1995.

[16] She was convicted on these grounds of violating two appellate orders dated 20 September 2005 and 6 April 2006 issued in the Slobodan Milosević case before the ICTY.

[citation needed] Most of the critical documents provided by Belgrade for the trial of Slobodan Milosević in relation to which confidentiality orders had initially been made were released by the ICTY and admitted as public evidence [when?]

[citation needed] In reaction to Hartmann's conviction by the ICTY, several international NGOs have criticized the ICTY for hiding its "legal reasoning" while the publicity of criminal proceedings is a general principle of criminal and international law which aim is to guarantee the transparency and public control of judicial proceedings.

[citation needed] Reporters Without Borders stated that "it is the duty of the press to highlight how this internationally created system of justice works, to question its procedures and to stimulate public discussion".

"[27] On 30 November 2011, Article 19 denounced the unlawfulness of the arrest warrant and "calls on all states, particularly the French and Dutch authorities, to avoid complicity in this perversion of international justice and to resist carrying out the order".