Crucial Terms and Definitions for Law Enforcement Personnel Explained

Basics of Law Enforcement Terminology

Law enforcement terminology, or lingo, refers to the specific and often colloquial terms and phrases used by police officers and other law enforcement officials during the course of their duties. The language of law enforcement is a form of industry slang, but can be difficult for even those outside of police work to understand due to the fact that many law enforcement professionals borrow freely from other fields of study, including accounting, linguistics, medicine and legalese, as well as their own vernacular . While some of this language is simply a short version that is easier to communicate, some terms have very specific meanings that can cause misinterpretation among those not in the field.
Bridging this communication divide is necessary, both for law enforcement professionals to be better equipped to handle their jobs and perform their duties effectively and safely, and for the general public to avoid miscommunications that could have serious consequences.

Common Terms Police Officers Use on the Job

Most people don’t know what all the terms the police use mean and why we use these often-misunderstood word groups. Below are some of these common terms:
Probable Cause
This is a legal term that means that the officer has a reason to believe that a crime is being committed or has been committed and that the person being arrested committed the crime. Anything that the officer has observed or believes to be true is enough to create probable cause to arrest. The legal term is not beyond a reasonable doubt but is something less—probable cause. For example, if an officer sees someone stealing a person’s purse, that is a crime in progress and is certainly probable cause for an arrest. If the officer believes that a person likely committed a crime and that person fled the scene, that too is enough to create probable cause for that suspect’s arrest.
Miranda Rights
The Miranda warning was part of a U.S. Supreme Court case in 1966 (Miranda v. Arizona) that held that since custodial interrogation could produce unreliable information about an alleged crime, the suspect would have to be informed of his or her rights. In order for the Fourth Amendment right against unreasonable searches and seizures not to be violated, a suspect must be informed that he has the right to remain silent and the right to an attorney, among other rights. Miranda rights only apply to those who are in custody and are being asked questions.
Perp
When the police say "perp," they are referring to the perpetrator of a crime. In other words, the criminal. When police are on a criminal investigation, they will refer to a suspect as the perp. For example, investigators might ask, "Is the perp in custody yet?" Another example might be officers discussing whether the perp is in another state. There is no better example than the famous quote, "Just one perp after another." A perp is simply a bad person who commits crimes.
Booking
When a person is arrested at the scene of a crime, they are taken into custody and booked. There is a procedure that must be followed. This includes verifying who that person is and where they live and collecting important information about the charges against them.

Specific Words Used by Law Enforcement Officials

A few common terms that law enforcers of all stripes should know:
Warrant: A warrant is a legal document issued by a court that allows law enforcement to, for example, search a suspect’s home or vehicle for evidence, or to take the suspect into custody. The warrant is an important protection for citizens and others against unwarranted searches. The warrant must be based on probable cause-meaning that the officer has reason to believe that the crime has occurred, or is about to occur.
Subpoena: A subpoena is a legal order requiring a person to appear in court. Subpoenas can also be used to compel a witness to produce, or disclose, relevant documents or evidence.
Affidavit: An affidavit is a written statement that is confirmed by an oath and signed by a notary public. An affidavit, as part of the application for a warrant, gives the court specific facts that support probable cause-that is, the crime has occurred, or is about to occur-to convince the court to issue the warrant.
Indictment: An indictment is a formal charge against a suspect that a crime has been committed. An indictment requires a grand jury, while an information does not. A jury trial in the United States begins with an indictment, or a charge, of guilt, just as the pre-trial process begins with a complaint. An indictment is a list of likely offenses against the criminal and those who may be called as witnesses. A complaint lists specific offenses, which may not be what ultimately ends up being charged. A grand jury generally sits continuously, as distinguished from a petit jury, or trial jury (although some states call the petit jury a "trial grand jury").

Jargon used in Crime Scene Investigations

Professional jargon has a way of creeping into law enforcement disputes and arguments. To avoid inadvertent errors or failures to timely raise unrefuted forensic evidence that is essential to the integrity of an investigation or case, lay persons need to have an understanding of some of the terminology that may be used during a crime scene investigation.
Forensics refers to the physical evidence or "forensic evidence" found at a crime scene. For example, in Jarman v. State, 607 S.W.3d 832 (2019) involving charges of aggravated assault, "Houston Police Department Crime Scene Investigator Maurice Martinez (Martinez) testified that his duties required him to ‘document the scene’ upon his arrival to the crime scene, and ‘[h]ave the documentation task force photograph, document evidence maybe that was located [sic] inside the scene . . . .’" There are other forms of forensics evidence, such as fingerprints or bloodstains, which are used as evidence at trial to help determine the perpetrator of the crime and to convict them. Errors can occur with collections of forensic evidence, hence, the importance of determining what procedures were followed by law enforcement, and if they were proper under the law.
The chain of custody is the process of maintaining the integrity of forensic evidence after it is collected at a crime scene. The chain of custody generally begins when a law enforcement officer is notified of a crime, travels to the crime scene, and collects the evidence. The chain of custody is a series of identity management techniques, procedures, and documentation practices to maintain and evaluate the integrity of the forensic evidence during transportation, receipt, examination, and storage. The forensic evidence must remain unaltered during the chain of custody. The chain of custody documentation includes information about when, where, how, and received who the evidence was transferred. When breaks in the chain of custody occur, there is question as to whether the evidence is reliable.
TBI, which stands for traumatic brain injury, is a form of forensic evidence found on some victims of aggravated assault. For example, in Jarman, mentioned above, "Dr. Bandopadhyay testified that [the victim] had injuries ‘principally to the head region’ and that her injuries were consistent with a mechanism of blunt force impact to the head."
CODIS is the Combined DNA Index System, which "fulfills the need for automated DNA index searching and matching on a State and National basis." It "has two separate indexes: the DNA Identification Index System (SDIS) is the core component, containing the DNA records of convicted offenders, unsolved crime scene evidence, and missing persons; the second component, National Offender DNA Database (NDIS), contains the DNA records of all convicted offenders and samples collected in unsolved crime scene investigations which were collected on or after January 1, 1994."
The inclusion of TBI and CODIS in the investigation of an aggravated assault is significant because if not initially investigated properly, these forms of forensic evidence may link a defendant to a "wrongful conviction," which occurs when the evidence was improperly relied upon or was obtained in violation of the defendant’s constitutional rights.

Terminology and Vocabulary used in Tactical Operations

Tactical Operations are typically of the highest profile of law enforcement operations. As the "point" law enforcement team, the importance of its planning and execution is emphasized. To that end, tactical operations are always conducted in accordance with their policies and procedures. When I say "always" I mean it. Deviations or exceptions to policies virtually always have a downside, sometimes a significant downside.
Those policies and procedures include use of terminology intended to describe concepts, strategies and implementation of missions of the Tactical Team and those with whom the Team often coordinates . There is not room here to explain all of the policies and procedures, but we’re going to take a look at some of the fundamental terminology used in tactical operations. It’s really a glossary of tactical terminology.
In this excerpt, we are examining terminology like: SWAT, Breach, Perimeter, Standoff, Tango, Rescue Task Force, BCT, FBO, Precinct, Strike Team, Blow the Door, A.K.A., 10-4, Assault Team, Roster, Vests, Time Hack, Wind-over-ground, MVU, SRT, Code Green, Inner Ring, Outer Ring, CBRNE, IO, Basic Plan, Red Cell, Vaccine, QRF, etc.
I am already working on my next post on the subject, more details on tactical terminology.

Common Law Enforcement Acronyms

For those interested in a slightly more complex legal language, law enforcement employs a number of commonly known acronyms.
Instructions, directions and clarifications from their employer are often sent by departments using these acronyms:
DUI (Driving Under the Influence): While it’s difficult to get an exact accounting of how many states have the DUI code, almost every state does recognize it. DUI is the most common acronym used, especially among police officers.
BOL (Be on the Lookout): This type of dispatch call usually accompanies information about a suspect vehicle or suspect. A BOL alert can be for any number of offenses, from drunk drivers to escaped prisoners. The reason the suspect is being look out for is largely up to the issuing department, and there is no standard format for a BOL broadcast.
NCIC (National Crime Information Center): The federal level of BOL has its own acronym – NCIC. An intergovernmental service operated by the Federal Bureau of Investigation, NCIC provides information about both people and property of interest to law enforcement officials, including stolen vehicles, escapees and wanted persons.
APB (All Points Bulletin): Almost synonymous with BOL requests, APB is a nationwide law enforcement bulletin that alerts all police departments to lookout for a car, person or other item of interest. These are most frequently used in cases where a person may have left the police district but is not a serious criminal suspect, such as in a burglary case or a person critically in need of medical attention.
Other standard terms for law enforcement include: 911, AOM, AR, MVA, CAD, ETA, ETO, FTT, FUBAR, IED, LOA, LIDR, MI, MVA, NDA, NLETS, NTA, PH6, POA, RPO, TTY, HPIOX and SO.

Final Thoughts and Further Reading

As we’ve seen, a range of law enforcement terms and vocabulary are commonly used in police, court, and correctional contexts. Knowing them can be essential to understanding what happens within these systems, particularly if you or a loved one comes into contact with law enforcement. [If that is the case, then insisting that your rights are honored is of vital importance. You or your loved one can enlist the help of a criminal defense attorney.] Moreover, these basic terms and phrases are often referenced in relevant law enforcement documents, which are sometimes used during follow-up legal proceedings .
While we’ve provided you with a few of the most common law enforcement definitions, this is by no means a complete list. Should you seek a deeper understanding of law enforcement terminology, we recommend checking out one of several online glossaries. These resources cover particular legal systems, such as the juvenile justice system, or track the evolution of law enforcement vocabulary over a period of time. The following additional resources will help you explore law enforcement terminology, current and historical.