Screenwriter J. Michael Straczynski first learned of the Christine Collins case in 1983 from a Los Angeles City Hall source who warned him about archive documents being destroyed, including transcripts of the city council welfare hearings on the case.

Straczynski spent about a year researching the case through archived criminal, courthouse, city hall and morgue records, gathering roughly 6,000 pages of documentation before writing the first draft of the script in just 11 days.

So the film could be credited as 'a true story' rather than 'based on' one, Straczynski went through the entire script with Universal's legal department, providing historical attribution for every scene.

Ron Howard originally optioned and intended to direct the film, but after committing to Frost/Nixon and Angels & Demons he had to step down; Howard and Brian Grazer then pitched the project to Clint Eastwood, who agreed to direct immediately after reading the script.

The film's title, referring to fairy folklore about a substituted child, was only meant by Straczynski as a placeholder title because of its supernatural connotations, but it was never changed.

Five actresses, including Reese Witherspoon and Hilary Swank, campaigned for the lead role, but Eastwood chose Angelina Jolie because he felt her face suited the 1920s period setting.

Jolie was initially reluctant to take the role because as a mother she found the subject matter distressing, and she ultimately based her performance on her own mother, who died in 2007.

Jason Butler Harner landed the role of Gordon Stewart Northcott after a single taped audition, and Eastwood was struck by how closely Harner resembled the real killer once in makeup.

Eastwood directed the film with an extremely economical style, rarely saying 'action' or 'cut', limiting rehearsals and takes, and speaking so quietly that camera operator Steve Campanelli sometimes had to relay his instructions to Jolie.

For scenes at the telephone exchange, Jolie learned to roller skate in high heels, replicating a documented practice from the period.

Principal photography finished two days ahead of its 45-day schedule, and much of the film was shot on the Universal Studios and Warner Bros. backlots rather than on real 1920s Los Angeles locations, since most original buildings had been demolished.

To keep up with Eastwood's fast shooting pace, the visual effects team largely avoided bluescreen in favor of rotoscoping, a technique Eastwood had also used extensively on Flags of Our Fathers.

Visual effects artists used motion-capture technology and the Massive crowd-simulation software to create digital pedestrians for 1920s Los Angeles street scenes, capturing twice as much motion data as on any previous project to allow close-up digital extras.

The film's final two-and-a-half-minute shot, in which Christine Collins walks off into a crowd, was not part of the Cannes screening version; visual effects supervisor Michael Owens added it afterward, inspired by the ending of Chinatown (1974).

Clint Eastwood composed the film's jazz-influenced score himself, which was orchestrated and conducted by Lennie Niehaus.