While watching a football match together, Veronica tells the Tattooed Boy that once she met Eric Cantona. Cate Blanchett and Cantona worked together in Elizabeth (1998).

The dance scene where Veronica dances with her family to "Everlasting Love" was added in on the spot by Cate Blanchett.

Composer Harry Gregson-Williams heard a boy (Brian O'Donnell) singing on the street for money in Dublin when he arrived to spend a few days on the set of the film. Later, he tracked the boy down again and recorded him singing six or seven folk songs acapella in a quiet alley. Gregson-Williams chose "Fields of Athenry" from the recording and added his own music around the song.

Jodie Foster was originally in talks to play the lead.

A daily Irish newspaper recently reported that Portlaoise prison (where John Gilligan and Brian Meehan are incarcerated) screens the movie at least once a month in the prison common hall at the request of the prisoners.

The Irish Film Censor, who passed the film with a 15PG (now defunct, but equal to 15A) certificate, acknowledged on the official Film Censor website, that had this film been fiction, or of any other plot source than it was, it would probably have received an 18 certificate.

Despite the fact that this was filmed in Super 35, "Filmed in Panavision" is listed in the end credits.

Joan Allen was set to star as Veronica Guerin when John Mackenzie was still attached to direct. Allen had already played a thinly veiled version of Guerin in When the Sky Falls (2000) which Mackenzie directed.

One of the characters in the film was based on the Irish gangster Martin Cahill, who was previously the subject of John Boorman's film The General (1998).

Danny DeVito was also considering the Veronica Guerin story as a directing project. He met with her family when he was in Dublin doing promotional work for Matilda (1996) and hoped to cast Winona Ryder in the role.

The red car driven by Veronica, throughout the movie, is an Opel Calibra sports coupe.