Terminology guide: what do all the Line of Duty acronyms mean?

Struggling to keep up with the police jargon in series six? We've got you covered.

Vicky McClure and Kelly Macdonald in Line of Duty

Do you know your ACC from your AC-12? And what on earth is an OCG? Line of Duty is back on our screens, currently airing series six, so it’s time to refresh our knowledge on the show’s police jargon, and embrace some new acronyms being used in the murder investigation of journalist Gail Vella, which is at the centre of the new series.


The jargon and acronyms can be tricky to get your head around – and not just for viewers, but for cast members too. Newcomer Kelly Macdonald, who plays DCI Jo Davidson, revealed that while it was tough learning the acronyms and their meanings, she developed a clever way to commit the letter sequences to memory.

“There would be certain acronyms that we would discuss at the time,” the actress told press before series six started. “In hair and makeup, they had a list pinned up, which was quite helpful, I found, of all the acronyms and what everything stood for. I’m not brilliant at [remembering them], but I sort of get by.”

Keeping track of all the acronyms they throw in is no picnic, especially since Line of Duty is sort of based on a real story, so we’ve produced a handy guide – check it out below.

Important acronyms for season 6

These apply to the murder investigation of journalist Gail Vella – aka Operation Lighthouse – being lead by DCI Jo Davidson. 

CHIS (covert human intelligence source)

MIT (murder investigation team)

OCG (organised crime group)

GSW (gunshot wound) 

PIM (post-incident manager)

NABIS (national ballistics intelligence service)

SFC (specialist firearms command)

Cuckooing – not strictly an acronym, but “cuckooing” refers to a crime in which drug dealers take over a vulnerable person’s home for use as a base

Production order – again, not strictly an acronym, but this is an order which requires a specified person must hand over materials to a police officer

Osman warning – once again, not strictly an acronym, but this is a warning of a death threat or risk of murder, issued by police if they become aware of a real and immediate threat to somebody’s life

Homozygosity – not an police acronym but a scientific term, referring to a genetic state where an individual has inherited the same DNA sequence for a gene from both their biological mother and their biological father. A high percentage of “runs of homozygosity” suggests a close family relationship between two individuals, or possibly even that they are the result of incest.

Police rankings:

It’s hard to keep up with police ranks and what they mean – Kate Fleming has gone from DC to DS to DI in the time we’ve known her. The below list is in hierarchical order:

DC – Detective Constable (cops who have passed their detective exams get a “D” instead of “P” before their rank)

DS – Detective Sergeant

DI – Detective Inspector

DCI – Detective Chief Inspector

Det Supt – Detective Superintendent

DCS – Detective Chief Superintendent

ACC – Assistant Chief Constable

DCC – Detective Chief Constable

CC – Chief Constable

Other police roles:

Ever felt a bit flummoxed by police roles? FI Tim Ifield? SIO Roz Huntley? Here’s a few acronyms you probably need deciphering… 

TFC – Tactical Firearms Commander

AFO Authorised Firearms Officer

SFC ­– Strategic Firearms Commander

CSECrime Scene Examiner

FI Forensic Investigator

FLO – Family Liaison Officer

FME – Forensics Medical Examiner

PCSO – Police Community Support Officer

SIO – Senior Investigating Officer

UCO – Undercover Officer

Commands and codewords:

“Fahrenheit” – Line of Duty’s codeword for “shoot to kill”. Different police operations use different codewords.

Status zero – Radio code, officer needs immediate assistance

Status five – Radio code, en route to incident scene

Status six – Radio code, on scene

Ten eight – Radio code, in service

TA (tactical advisor)

Other acronyms:

“OCG” is a term you hear bandied around a LOT in Line of Duty – here’s an explanation of what it means, plus a load of other handy police terms:

AC-12 – Anti-Corruption Unit 12

ARU – armed response unit

PNC (police national computer)

CPS – Crown Prosecution Service

DIR – digital interview recorder

DPS – Directorate of Professional Standards

ED905 – this is just an arbitrary code. In series five it represents a truck load of heroin. 

IRV – incident response vehicle

MoPI – Management of Police Information

PR – police regulations

Reg 15 – Regulation 15 notice. Advises an officer that a complaint has been made or a matter has come to light about them that warrants an investigation.

RUC – Royal Ulster Constabulary, the police force in Northern Ireland from 1922 to 2001. AC-12 chief Ted Hastings served in the RUC during his days as a constable.

RTC – road traffic collision

SCG – serious crime group

Sitrep – situation report

Be sure to check out our Line of Duty episode 4 recap for all the details, including our character profiles of Terry Boyle and Carl Banks.


Line of Duty returned on Sunday 21st March at 9pm on BBC One. Read our comprehensive  Line of Duty recap to refresh your memory on all that has happened so far. Looking for something to watch? Check out our handy TV Guide.