Giallo is a genre of Alfred Hitchcock-style murder mystery most common in 1970s Italian films. The word is Italian for "yellow," which refers to the color of the cheap paper on which lurid Italian detective fiction was printed. This is the same meaning that "pulp fiction" would have in the US.
Most gialli have a similar plot structure. A serial killer is in operation, and his targets are usually beautiful, young women. "His" targets: The killer is usually male, but not always. Don't Torture a Duckling and Who Saw Her Die are notable examples in which the victims are children. Murders tend to be bloody, sadistic and spectacular. All that is usually seen of the killer is a hand that wears a black glove and carries a weapon. This weapon is usually a knife, but killers will use any available object. The choices of murder weapon can be very inventive and may carry an element of humor.
Mysteries allow their readers and viewers to test their deductive skills by trying to guess the identity of the killer. Gialli make this a plot element: The protagonist is typically a private citizen who carries on an investigation separately from the police He may be a suspect who is acting to clear his own name, may have ties to one of the victims, or may simply have time on his hands and an interest in the case. He may have difficulty convincing the police of the existence of or the connection between the crimes. "He" again: The main character is usually a man and usually works together with a woman.
Killers in gialli tend to have some kind of revenge motive. The discovery of this motive is usually the key to revealing the killer's identity. This contrasts with most slashers and psycho-shock films, where the murderer often is simply "ax-crazy." Revenge may be a factor in slashers, but there it usually takes place a generation later and against people who had no connection to the original event. Gialli are set within a couple of years of the original incident, and their killers target people who were directly involved.
Giallo is often said to have begun with Mario Bava's The Girl Who Knew Too Much and Blood and Black Lace. These are mysteries in the vein of Hitchcock, especially his Psycho, but they emphasize fear and violence over suspense and investigation. This fear element effectively makes them horror movies structured as mysteries. If their sexual content is especially pronounced, then gialli may cross over into the Eurosleaze genre. Strip Nude for Your Killer would be one such example.
Dario Argento is perhaps the defining director of the genre, thanks to his work up to and including Deep Red, and he still films gialli. Many Italian directors filmed gialli during the early 1970s, including many such as Lucio Fulci and Umberto Lenzi who are more commonly associated with other genres. There is debate over whether an American giallo could exist. Brian De Palma's Dressed to Kill is generally considered to be the most successful attempt.
Gialli are mysteries in the Hitchcock tradition, though they delight in levels of explicit sex and violence that he would only have hinted at. Like the slasher, the giallo is a very recognizable genre. Trademark giallo features include: mysterious flashbacks to an earlier trauma; close-up shots of killers' gloved hands; bloody, shocking and sadistic violence, often directed at beautiful women who tend to wear less than their slasher counterparts; decadent, wealthy characters with hidden secrets; ineffective police who welcome the protagonist's amateur detective efforts; highly saturated colors, and red herrings galore.
Gialli are detective mysteries, but they rarely, if ever, involve street-level crime. Their characters live in hip, stylish, expensive-looking dwellings. Protagonists frequently have some kind of ties to the art or fashion worlds. Deep Red's protagonist is a pianist, and artwork figures heavily in its plot. Strip Nude for Your Killer is set in a modeling agency. The protagonists of Tenebre and The Bird With the Crystal Plumage are both writers. It is common for the main character to be a visitor, often from America. The Girl Who Knew Too Much and many of Argento's films use this device.
Gialli may contain a light supernatural element such as a character who is psychic or a witch. The events of The Girl Who Knew Too Much are precipitated when a character witnesses a murder that occurred ten years prior. The protagonist of Phenomena has a psychic bond with insects. A witch is a central character in Don't Torture a Duckling.