Ten general features characterize the police procedural. I say "general" because the sub-genre has greatly diversified, from urban and rural, anglo and ethnic, coarse and cultured, low-brow and literary, humorous and gritty, and combinations thereof. Even so, here we go with the first 5:
1. In police procedurals, cops are average people: normal, but nervous.
They have stomach trouble, problems with their kids, their teeth, and their finances. When they meet horror, they puke. When threatened with death, they lose bladder control. They worry about getting their suit cleaned if a crook bleeds on it. They struggle with their marriages. Many cops are not just 'average' but 'common' and lower class. They read cheap novels when goofing off, joke in adolescent ways, and eat greasy junk. Cops reflect the tastes and values of the working class, the traditional source of recruits. The college-educated are few; cops often insult "eggheads." Cop heroes are not dumb, but they believe intellectuals are unfit for their work. They often solve crimes by accident, by their dogged routine, or by the fact that criminals are stupid.
I know, you're already thinking of tons of exceptions. Like I said, the field has diversified--and deepened.
2. Police work is communal and cops do not work alone.
More than one officer works a case and more than one shift of workers gathers and sorts evidence. The individual cop depends on others: lab people, record keepers, ballistics experts, etc. Many officers work on many cases simultaneously.
Even so, there is usually one central figure who resembles the hard-boiled detective. That cop is usually tough and action-oriented. They talk in clipped, wise-cracking ways. They are often alienated from families. Their real family is the station, where the group pulls together and protects its own. As a class, they have their own jargon and low-humor jokes. They deal with human garbage and filth more degrading than hardboiled private detectives, who are sentimental about it or above it. Their lives are dangerous and uncertain, and they resemble soldiers on the front line more than anything else. Many real cops are, indeed, former soldiers. And many police departments have become highly militarized.
3. Police work routines shape characters.
The principal technique is to show what cops really do day-to-day: how shifts are are assigned, how records are kept, how evidence is labeled and filed, and so on. Stress, boredom, dealing with the depraved, facing terror: all in a day's work and for lousy pay.
4. Police work is unrewarding.
Cops are underpaid for dangerous work and promotions are often a matter of who you know, not how well you do your job. Corruption, not competence, is key. Good cops are out making arrests, not studying for promotion exams. Upper echelon officers are political brown-nosers and bootlickers or moronic efficiency experts. Procedurals emphasize the drudgery and difficulty of staying motivated. And the public often distrusts the police.
5. On top of being unrewarding, police work is boring and repetitive.
The problem for writers is how to show actual police work in all its mundane mechanical-ness and still keep a reader. Most of the work is trivial and routine. Most crimes are simple, not intricate puzzles: victims knew their attackers, the criminals are stupid and careless. They are not urbane and educated like in Christie's privileged world.
To get around this, writers turn to showing how the police bureaucracy fouls things up so much that it's a wonder crimes get solved at all. The anonymity and complexity of the city especially complicates easy cases and provides for atmosphere and a wealth of curious characters. Rural crime novels have plenty of quirky characters, too, but instead of anonymity you get complicated family webs where everyone knows everybody else.
Another way writers get around the routine is to present many officers working on many cases at once, presenting the chaos of real police stations. Even small town stations get overwhelmed. No Mayberry here. McBain shows lots of reports and forms, not so much to develop the plot or solve the crime but to add to the feeling of leg work and paperwork required.
A third common alternative is to emphasize the squalor and most gruesome crimes (this is true for both urban and rural crime fiction). Arbitrary violence, mutilated corpses, rotting bodies, oozing organs: the details are presented matter-of-factly. No cozy 'body in the library' here. Forensic detail is important: pieces of brain, descriptions of exit wounds, post-mortem excretion, severed limbs, and so on. Police see people at their worst: the victimized, the destitute, the deranged. Grieving parents, hostile witnesses, creepy criminals fil the day. Police deal with the leg work and paperwork to solve the heinous crimes the cozies never touch: rape, torture, child abuse.
On that note, we'll pause for next time when I'll list the last 5 chief characteristics of cop procedurals.
