Witnesses

The show is the fourth collaboration between creators Hervé Hadmar and Marc Herpoux, following Les Oubliées (2008), Pigalle, la nuit (2009) and Signature (2011).

Hadmar got the idea to set the series in Le Tréport while on a romantic weekend there with his wife, immediately linking the show homes to childhood memories that used to frighten him, and calling Herpoux to develop the concept as a French version of The Killing.

The creators deliberately cast Thierry Lhermitte, a well-known actor, against type as the old cop, while pairing him with Marie Dompnier, a then-unknown actress, to embody the classic veteran/newcomer police duo dynamic.

For the second season, Catherine Mouchet's role as commissioner Maxine Dubreuil was taken over by Judith Henry, and Mehdi Nebbou's character Eric was recast with Guillaume Durieux.

Season 1 was filmed over 78 days on a budget of 7 million euros, shooting from mid-December 2013 to April 2014 in the Nord department (Douai, Dunkerque) and in Le Tréport, Normandy.

A former Banque de France building in Armentières was transformed into a police station set for two weeks of filming, and a prison scene in the second episode was shot in the real, disused Loos-lez-Lille prison, built in the 19th century and later demolished.

Season 2 filming began on 28 March 2016 at Mont-Saint-Michel and its surroundings, including Avranches town hall, before moving to Lille and the Opal Coast.

The opening theme song is 'We Don't Die' by Tricky, featuring Francesca Belmonte.

Marie Dompnier won the Golden FIPA award for best actress in a television series at the 2015 Biarritz International Festival of Audiovisual Programming for her role as Sandra Winckler.

The series was sold to UK's Channel 4, marking the first time in 20 years that a France Télévisions series was broadcast in the United Kingdom, and it also began streaming with subtitles on Netflix in the United States from 1 May 2015.

Ahead of the first season's premiere, an official website filled with clues was launched in February 2015, including an online treasure hunt allowing viewers to discover the first episode in advance.

To coincide with the season 2 release, an immersive escape-game experience using a virtual reality headset was set up at La Pièce and later relocated to the Centquatre venue.