Both krimi and giallo exhibited a high degree of self-reflexivity early on:
In The Girl Who Knew Too Much the protagonist is immediately established as a reader of mysteries and subsequently endeavours to use her generic knowledge to solve the one within which she finds herself embroiled.
In The Indian Scarf the comic ending – which is admittedly somewhat at odds with the proceedings to that point – sees the plot being described as being worthy of Edgar Wallace himself.
In The Squealer the female lead is a thriller writer, the first chapter of whose latest work contains no less than eight murders to top Wallace's own three. ("I am going to give them crime and blood and three murders to the chapter. Such is the insanity of the age that I do not doubt for one moment the success of my venture.")
This distinguishes them from the slasher film, where similar techniques only became commonplace (or at least recognised when we consider something like Saturday the 14th as forerunner of Scary Movie) with Scream and company in the 1990s.
The paradigmatic investigator within the krimi is a Scotland Yard detective whose involvement in the case is a professional one; that of the giallo is an amateur who finds him or herself unwittingly involved as witness to a crime or suchlike.
While these are not absolutes, the exceptions to them, such as the giallo What Have You Done to Your Daughters, very much prove the rule.
Although some gialli, such as Who Saw Her Die and Don't Torture a Duckling, depend upon their specific locations, most could be placed within any Italian conurbation, as demonstrated by Argento's using Turin to double for Rome in Deep Red.
Almost every krimi emphasises its location - almost invariably London and its surrounds - to a far greater extent. Shots of the Houses of Parliament, Picadilly Circus, The Tower of London and other signifiers or Londonicity are omnipresent.
Within gialli the majority of killers are “motivated” by insanity, followed by revenge and financial gain. Within the krimi these propensities are reversed.
As a result of this the krimi would seem to be less susceptible to obvious psychoanalytic interpretation, with this perhaps being one factor that has contributed to its comparative neglect.
The relationship with the literature
Though taking its name from the literary form, the giallo film seems to exist as something separate. Straight adaptations are rare.
In the krimi the Edgar Wallace name and source novel are far more important, signalled by the “Hello this is Edgar Wallace speaking” introductions; the Edgar Wallace credit alongside the title of the film and the cast / crew credits, and the identification of which particular Goldmann's taschenkrimi the film is adapting. (I suspect this is more pronounced in the early 1960s Wallace adaptations than those of his son, Bryan Edgar Wallace, later in the decade, but have not seen enough of the latter to really confirm or refute this hypothesis.)