Glossary - My ever expanding list of acronyms and cop talk.

Cops have their own language.  Much of that cop talk is localized by various legal codes, radio codes, and acronyms.
On this page, I will continue to add the various terms I mention in my blog.  Check back often, as it's a work in progress.
LEGAL TERMS AUTHORS SHOULD KNOW
(that are commonly misunderstood)
Mayhem - is unlawfully, under circumstances manifesting extreme indifference to the physical or psychological well-being of another person, intentionally causing permanent disability or disfigurement of another human being or depriving a human being of a limb, organ, or member of his or her body.  (See California Penal Code Section 205.)
Mayhem is NOT some sort of uproar; that is bedlam.
Molest - as in child molestation (California Penal Code section 647.6) is NOT the same as lewd or lascivious acts with a child (California Penal Code Section 288(a) .) 
You "annoy" or "molest" a child when you engage in conduct likely to disturb or irritate a child under 18 years of age, and your conduct is motivated by sexual interest in a specific child or in children generally.  Under Penal Code 647.6, you do not need to touch any part of a child's body. You may violate this section with inappropriate language, or by engaging in otherwise innocent conduct…such as masturbating…if your intent is that your actions be observed by a child or children.

RADIO CODES
NOTE:  Most radio codes are specific to a local area and are NOT standardized across the state or country.
Code 1 - Respond at your convenience. 
Code 2 - Urgent Response (Respond directly to this call, but lights and siren are NOT authorized.)
Code 3 - Emergency Response (lights and siren)
Code 4 - No further assistance necessary. Radio code for "I'm okay and don't need backup."  Officers will often use four fingers as a sign language version of Code 4 to their partner that everything is under control.
Code 7 - Lunch break  (It's still lunch if you're eating at 0300.)
ACRONYMS
CAD - Computer Aided Dispatch (the software loaded on an MDT or MDC)
DRT - an unofficial acronym for "Dead Right There."
GOA - a common acronym used on the radio for "Gone On Arrival"
HUA - an unofficial acronym for "Head Up Ass."
MDC or MDT - Mobile Data/Digital Terminal or Mobile Data/Digital Computer (the computer in the police car connected to CAD)
NHI - an unofficial and derogatory acronym for "No Humans Involved." 
NOR - NO Report (the opposite of RTF.)
RTF - Report To Follow (this often prompts Dispatch to assign a case number to the call.)
UTL - Unable To Locate (similar to GOA.)
LEGAL SECTIONS
187 - The California Penal Code section for murder. (Link to the actual law: 187 PC)  This is a section of STATE law.  If your story is occurring somewhere outside of California, you probably shouldn't refer to a murder as a 187 as other states have differing penal code sections for murder.
5150 - Similar to the 187 section mentioned above, 5150 is specific to California.  5150 is a section of the Welfare and Institutions code (Link to the actual law: 5150 W&I) that authorizes an involuntary 72-hour hold for psychological observation when the person is a danger to himself or others (i.e. showing suicidal or homicidal tendencies.)
COP SLANG
Like slang in any other culture or subculture, it varies by region or even by Department.  This list is a work in progress...
Adam-Henry - the phonetic abbreviation for A.H., meaning:  a$$#0le
Black & White - A marked patrol car.  (Also called: Cruiser, Unit, Radio Car) 
BFE - In the middle of nowhere. (Bum F*ck Egypt)
H.M.F.I.C. - Head Mutha F**ker In Charge - usually the Sergeant or Lieutenant in the field.
Plain Wrap - unmarked police car (Also called: G-Ride, U/C Ride)  See the note below under: U-Boat.
Roll Code - drive with lights/siren (Code 3)
Slick Top - A marked patrol car without a light bar on the roof.
Stop & Rob - a convenience store
U-Boat - A report writing car, usually one rookie officer.  (Some agencies call an undercover car a U-Boat, but not in Southern California.)