Detective Allen Sliver squinted through his taped-up glasses at the forensic evidence from the heist, and agreed it seemed to be an open-and-shut case. The bank manager's shifty son's fingerprints were all over the safe, and his night-at-the-symphony alibi wasn't checking out. Sliver knocked a stack of papers onto the floor as he leaned over the desk, drawing stares from the nattily dressed bank employees. Sliver loved uncomplicated cases, but as for those triat were too easy.

.. they gave him indigestion.
Sliver plucked an antacid pill from his overcoat pocket, scratched his rumpled hair, and failed to suppress a burp, drawing more stares. The rumpled detective pondered what his gut was trying to tell him.
What aspect of this passage is common to much crime/detective fiction?
A number of potential suspects are alluded to who will be further developed later on.
The use of dark imagery paints a sense of imminent danger around the detective.
It presents an unlikely main character who appears to be clumsy and unqualified.

The presentation of an unlikely main character who appears to be clumsy and unqualified.

The aspect of this passage that is common to much crime/detective fiction is the presentation of an unlikely main character who appears to be clumsy and unqualified.

The answer to the question is "It presents an unlikely main character who appears to be clumsy and unqualified."

In this passage, Detective Allen Sliver is portrayed as a rumpled, clumsy, and unorthodox character. He wears taped-up glasses, drops papers, scratches his rumpled hair, and even burps in public. These characteristics make him seem unlikely to be a skilled and competent detective. This portrayal of the detective as an unconventional and flawed protagonist is a common aspect of crime/detective fiction. It adds an element of intrigue and unpredictability to the story, as readers are often drawn to flawed characters who must overcome their personal quirks and obstacles to solve the crime.