After seven weeks of high drama and some pretty irresistible cliffhangers, the sixth season of Line of Duty has finally reached its end. That means we can say goodbye to our police term glossaries – at least for now.


As with every previous season of the show, the most recent run was full of complex acronyms and unfamiliar police jargon, with AC-12 constantly mentioning OCGs, ACCs, CHISs and all the rest of it.

If you're in need of a bit of a refresh regarding some of the terms used during the series, you can check out the handy guide we've produced below, which includes all the major police rankings, some commands and codewords and every other acronym that has played a major part in the show.

Important acronyms for season 6

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

FI (Forensic Investigator)

AMO (addiction medical officer)

VPU (vulnerable prisoner unit)

GPR (ground penetrating radar)

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)

Blue Ticket – Another term for a police officer's firearms licence, which allows them to carry a gun.

Dry cell – A room that prisoners are placed in, that lacks any plumbing facilities, to avoid disposal of evidence.

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

DSU - 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 are a few acronyms you probably need deciphering...

TFC - Tactical Firearms Commander

AFO - Authorised Firearms Officer

SFC ­– Strategic Firearms Commander

CSE - Crime 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


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 tonight? Check out our handy TV Guide.