Design a movie poster for a legal thriller titled 'The Last Witness'. The central focus is a tense courtroom scene. In the background, shadowy figures representing justice, such as a judge's gavel and scales, are subtly incorporated into the dark, stormy sky. In the foreground, a lone, determined witness stands at the center, their silhouette illuminated by a harsh spotlight. The witness's face is partially obscured, adding a sense of mystery and tension. The color scheme is dominated by dark blues and grays, with contrasting sharp whites and deep reds to highlight the title and key details. The tagline 'Truth is the only defense' should be prominently displayed at the bottom in a bold, serif font.