Nao Omori who plays the lead role of the character Koichi Saeki has family in the movie business. His father Akaji Maro was in many movies (for example the Kill Bill movies). His brother Tatsushi Omori directs movies.
The 2004 novel was originally called "The Singing Policeman" (Utau Keikan). "Singing" is inside police slang for confessing and leaking information about the internal goings on of the police. However the title was changed to the "The Laughing Policeman"(Warau Keikan) due to perceived confusion by the public.
The director Haruki Kadokawa said that he used jazz music as the tempo provided time for the characters to talk and let what they say sink in. A fast soundtrack, as is used on some TV police suspense shows, have caused an unwanted speeding up of the dialogue.
SAT, or Special Assault Team, are a part of the Japanese police that act as a response team to crimes like terrorism. In the movie they are assigned to shoot Suguru Tsukui (and thus prevent him from testifying).
A part of the plot was inspired by the 2002 Inaba Incident which was a scandal that involved the Hokkaido Prefectural Police. A former police inspector, Yoshiaki Inaba, had been charged in possession of a gun and stimulants. In his defense his legal team argued that Inaba had been backed high ranking police officials.