Barrister Sir Wilfrid Robats (Charles Laughton) is discouraged from taking "strenuous" criminal cases after a heart attack. Yet he can't resist defending Leonard Vole (Tyrone Power), accused of murdering a middle-aged benefactress (Norma Varden). The evidence seems stacked against Vole, with the prosecution calling Leonard's wife Christine (Marlene Dietrich) as a surprise witness. Then an anonymous informant gives Sir Wilfrid evidence that demolishes Christine's credibility... or does it?
Witness for the Prosecution cleverly plays against expected genre tropes. Leonard has evidence and motive weighing against his seeming earnestness. And Christine's untrustworthiness gradually piles up, from her experience as an actress to revelations about a past marriage. For all Sir Wilfrid's legal wrangling, he's reduced to a pompous pawn. Agatha Christie's surprise witnesses and last-minute revelations make more dramatic than legal sense, yet Witness is so absorbing we don't mind logical holes.
Wilder's craftsmanship is peerless, from his straightforward direction to the screenplay. He sprinkles in sparkling dialogue, while folding in digressive episodes like Vole's meeting Christine in postwar Germany. Between trial scenes, Wilder gets great mileage out of Sir Wilfrid's quirks and health concerns; he flashes Vole with a monocle to unnerve him, while bickering with a nurse (Elsa Lanchester) over cigars and lift chairs. Many Wilder films fall down in the last act, but Witness's final twist is a genuine shocker.
Charles Laughton dominates Witness with acerbic intelligence and exasperated wit. He sparkles both in heavy courtroom scenes and light banter with Elsa Lanchester's fussy nurse. Marlene Dietrich puts her sensual hauteur to great use; her icy dignity clashes with Christine's unreliability. Tyrone Power mixes seedy charm and exaggerated anguish. Una O'Connor (The Informer) has a standout role as an unreliable witness. Wilder casts distinguished players like John Williams (Sabrina), Henry Daniell (The Sea Hawk) and Torin Thatcher (Mutiny on the Bounty) in minor roles.
Witness for the Prosecution brilliantly sends up expectations. We anticipated a straightforward legal procedural, until Wilder pulls the rug out from under us. For those tired of standard courtroom dramas, Witness is a delectable treat.