However, amongst English-speaking fans of the cinema of the fantastique and cult film fans, the term 'giallo' is often used in a slightly different context, to refer to a particular style of (predominantly Italian-produced, though often the product of international co-productions) murder mystery films which often (but not always) include elements of horror fiction and eroticism (similar to the French fantastique genre). These films often contained explicit violent or sexual content, as a result of the relaxation of attitudes towards film censorship during the 1970s. However, they may also be much more restrained in their style and approach: for example, in films such as Le orme (Luigi Bazzoni, 1975).
The word "giallo" is Italian for "yellow" and its use as a label denoting that a film or novel is a 'thriller' derives from its association with series of cheap paperback mystery novels, published in Italy in the 1940s and beyond, which were adorned with trademark yellow covers.
Published as cheap paperbacks, the success of the "giallo" novels soon began attracting the attention of other publishing houses, who began releasing their own versions, mimicking the yellow covers. The popularity of these series eventually established the word giallo as meaning a mystery novel.
For Italian audiences, giallo has come to refer to any kind of thriller, regardless of its origin. Thus, American, British or other thrillers such as Psycho, Vertigo or Peeping Tom are considered gialli. For English-speaking audiences, however, the term has over time come to refer only to a very specific type of Italian-produced thriller which Italian audiences have historically referred to as "thrilling all'italiana" or "spaghetti thrillers."
The term giallo first referred to similarly themed crime and mysterypulp novels with yellow covers which became popular in post-fascist Italy. The film subgenre that emerged from these novels in the 1960s began as literal adaptations of the books, but soon began taking advantage of modern cinematic techniques to create a unique genre which veered into horror and psychological thrillers. The giallo film genre proved to be a major influence on the later slasher film genre.
There is some critical disagreement on exactly what elements comprise a giallo film. Critic Gary Neednam, considering the problem, writes:
"By its very nature the giallo challenges our assumptions about how non-Hollywood films should be classified, going beyond the sort of Anglo-American taxonomic imaginary that "fixes" genre both in film criticism and the film industry in order to designate something specific. ...however, despite the giallo's resistance to clear definition there are nevertheless identifiable thematic and stylistic tropes."
These distinct "thematic and stylistic tropes" constitute a loose definition of what this sort of film entails.
Although often based around crime and detective work, gialli should not be confused with the other popular Italian crime genre of the 1970s, the poliziotteschi, which refers to "tough cop", action-oriented films (largely influenced by Dirty Harry, The Godfather, and The French Connection). Directors and stars often moved between both genres, and some films could be considered under either banner, such as Massimo Dallamano's 1974 film La polizia chiede aiuto (What Have They Done to Your Daughters?). Nevertheless, most critics agree that gialli represent a separate and distinct category with unique features.
The poster for 1971's La tarantola dal ventre nero (Black Belly of the Tarantula) depicts many common icons of the giallo: a mysterious gloved hand with a knife, a beautiful female victim, intense stylized color, and a titular reference to an animal.
Giallo films are generally characterized as gruesome murder-mystery thrillers that combine the suspense elements of a Hitchcock film with scenes of shocking horror featuring excessive bloodletting, stylish camerawork, and often jarring musical arrangements. The standard plot, used in countless films, involves a mysterious, black-gloved psychopathic killer who stalks and butchers a series of beautiful women. While most gialli involve a human killer, some also feature a supernatural element. The typical giallo protagonist is an outsider of some type, often a tourist, and usually a young woman (gialli rarely feature law enforcement officers as chief protagonists, which would be more characteristic of the poliziotteschi genre). They are generally unconnected to the murders before they begin, and are drawn to help find the killer through their role as a witness to a crime. The mystery centers on the identity of the killer, who is frequently revealed to be another key character who had concealed his or her identity with a disguise consisting of some combination of hat, mask, sunglasses, gloves, and trench coat. Thus, the literary whodunit element of the giallo novels is retained, while being filtered through Italy's longstanding tradition of opera and staged grand guignol drama.
The killings are invariably violent and gory, featuring a wide variety of explicit and imaginative death. Frequently (though not always), the murders will take place from the first-person perspective of the killer, with the black-gloved hand holding a knife being presented from the killer's point of view, arguably adding an element of voyeurism. These murders often occur when the victim is most vulnerable (showering, taking a bath, or scantily clad). As such, giallo films often include liberal amounts of nudity and sex, with several actresses becoming strongly associated with the genre including Edwige Fenech, Barbara Bach, Daria Nicolodi, Barbara Bouchet, Suzy Kendall, Ida Galli, and Anita Strindberg. The association of female sexuality and brutal violence has led some commentators to accuse the genre of misogyny.
Gialli are noted for psychological themes of madness, alienation, sexuality, and paranoia. The protagonist is usually a witness to a gruesome crime, but frequently finds their testimony subject to skepticism from authority figures, leading to a questioning of their own perception and authority. This ambiguity of memory and perception can escalate to delusion, hallucination, and delirious paranoia. Since this witness is typically a woman, this can also lead to what writer Gary Needham calls, "...the giallo's inherent pathologising of femininity and fascination with "sick" women." The killer is likely to be mentally ill as well; giallo killers frequently have gone mad due to some past trauma, often of a sexual nature (and sometimes depicted in flashbacks). The emphasis on madness and subjective perception has roots in the giallo novels (for example, Sergio Martino's Your Vice Is a Locked Room and Only I Have the Key was explicitly based on Edgar Allan Poe's short story story "The Black Cat", which deals with a psychologically unstable narrator) but also finds expression in the tools of cinema: The unsteady mental state of both victim and killer is often mirrored by the wildly exaggerated style and unfocused narrative common to many gialli.
Writer Mikel J. Koven posits that gialli reflect an ambivalence over the social upheaval modernity brought to Italian culture in the 1960s. He writes,
"The changes within Italian culture... can be seen throughout the giallo film as something to be discussed and debated -- issues pertaining to identity, sexuality, increasing levels of violence, women's control over their own lives and bodies, history, the state -- all abstract ideas, which are all portrayed situationally as human stories in the giallo film.
Gialli have been noted for their strong cinematic technique, with critics praising their editing, production design, music, and visual style even in the marked absence of other facets usually associated with critical admiration (as gialli frquently lack characterization, believable dialogue, realistic performances, and logical coherence in the narrative). Writer Alexia Kannas argues of 1968's La morte ha fatto l’uovo (Death Laid an Egg) that "While the film has garnered a reputation for its supreme narrative difficulty (just as many art films have), its aesthetic brilliance is irrefutable," while critic Leon Hunt writes that frequent gialli director Dario Argento's work "vacillate[s] between strategies of art cinema and exploitation.".
Gialli are frequently associated with strong technical cinematography and stylish visuals. Critic Maitland McDonagh describes the visuals of Profondo rosso (Deep Red) as, "vivid colors and bizarre camera angles, dizzying pans and flamboyant tracking shots, disorienting framing and composition, fetishistic close-ups of quivering eyes and weird objects (knives, dolls, marbles, braided scraps of wool)..." In addition to the iconic images of shadowy black-gloved killers and gruesome violence, gialli also frequently employ strongly stylized and even occasionally surreal uses of color. Directors Dario Argento and Mario Bava are particularly known for their impressionistic imagery and use of lurid colors, though other giallo directors (notably Lucio Fulci) employed more sedate, realistic styles as well. Due to their typical 1970's milieu, some commentators have also noted their potential for visual camp, especially in terms of fashion and decor.
Music has been cited as a key to the genre's unique character; critic Maitland McDonagh describes Profondo rosso (Deep Red) as an "overwhelming visceral experience...equal parts visual...and aural."  Writer Anne Billson explains, "The Giallo Sound is typically an intoxicating mix of groovy lounge music, nerve-jangling discord, and the sort of soothing lyricism that belies the fact that it's actually accompanying, say, a slow motion decapitation," (she cites as an example Ennio Morricone's score for 1971's Four Flies on Grey Velvet).Composers of note include Morricone, Bruno Nicolai, and the Italian band Goblin (all three of whom are probably best known for their collaborations with director Dario Argento, though they worked with other directors as well). Other important composers known for their work on giallo films include Riz Ortolani (composer for La ragazza dal pigiama giallo (The Girl in the yellow Pajamas)) and Fabio Frizzi (Sette note in nero aka The Psychic).
The first giallo novel to be adapted for film was James M. Cain'sThe Postman Always Rings Twice, adapted in 1943 by Luchino Visconti as Ossessione. Though the film was technically the first of Mondadori's giallo series to be adapted, its neo-realist style was markedly different from the stylized, violent character which subsequent adaptations would acquire. Condemned by the fascist government, Obsessione was eventually hailed as a landmark of neo-realist cinema, but it did not provoke any further giallo adaptations for almost 20 years.
In addition to the literary giallo tradition, early gialli were also initially influenced by the German "krimi" films of the early 1960s that were based on Edgar Wallace stories. These black-and-white films typically featured whodunit mystery plots with a masked killer, but despite their link to giallo author Wallace they also featured little of the excessive stylization and gore which would define Italian gialli (though some giallo regulars, such as composer Ennio Morricone and director/cinematographer Joe D'Amato, did work on later krimi films following their successes in Italy). Strong parallels exist, though; a particularly good example is The Monster of London City (1964) which seems almost like a prototype of the Italian giallo in every aspect. The Swedish director Arne Mattsson has also been pointed to as a possible influence, in particular his 1958 film Mannequin in Red. Though the film shares stylistic and narrative similarities with later giallo films (particularly its use of color and its multiple murder plot), there is no direct evidence that subsequent Italian directors had seen it.
Dario Argento's first feature, The Bird with the Crystal Plumage (1970), was greatly influenced by Blood and Black Lace and introduced a new level of stylish violence and suspense that helped redefine the genre. The film was a box office smash and was widely imitated. Its success encouraged a frenzy of Italian film makers to shoot more colorful and gory films. Soon the giallo became a genre of its own, with its own rules and with a typical Italian flavor: adding additional layers of intense color and style. The term "giallo" finally became synonymous with a heavy, theatrical and stylized visual element.
The genre had its heyday from 1968 through 1978, with dozens of films released. The most prolific period however was the three-year timespan between 1971 and 1973, during which time 65 different gialli were produced (see filmography below). Among the directors represented with notable works in this genre are Mario Bava, Dario Argento, Lucio Fulci, Sergio Martino, Paolo Cavara and Umberto Lenzi.
Gialli continued to be produced throughout the 1970s and 1980s, but gradually their popularity diminished and film budgets and production values began shrinking. Director Pupi Avati satirized the genre in 1977 with a slapstick giallo titled Tutti defunti... tranne i morti.
Though the giallo cycle waned in the 1990s and saw few entries in the 2000s, they continue to be produced, notably by Argento (who in 2009 released a film actually titled Giallo, somewhat in homage to his long career in the genre) and co-directors Hélène Cattet & Bruno Forzani, whose Amer (which uses music from older giallis, including tracks by Morricone and Bruno Nicolai) received a positive critical reception upon its release in 2009. To a large degree, the genre's influence lives on in the slasher films which became enormously popular during the 1980s and drew heavily on tropes developed by earlier gialli.
The giallo cycle has had a lasting effect on horror films and murder mysteries made outside of Italy since the late 1960s. This cinematic style and unflinching content is also at the root of the gory slasher and splatter films that became widely popular in the early 1980s. In particular, two violent shockers from Mario Bava, Hatchet for the Honeymoon (1970) and Twitch of the Death Nerve (1971) were especially influential.
^Olney, Ian (February 7, 2013). Euro Horror: Classic European Horror Cinema in Contemporary American Culture (New Directions in National Cinemas). Indiana University Press. pp. 36, 104, 117. ISBN025300652X.