In the most widely used version of police radio codes, the 10-99 police code meaning is “wanted or stolen indicated” — a signal that a person or vehicle just run through dispatch came back with an active hit in a law enforcement database. That is the closest thing to a standard definition, but 10-codes are inconsistent from agency to agency, and 10-99 can mean something entirely different depending on which department is transmitting it.
The Standard APCO Meaning
The expanded code list developed by the Association of Public-Safety Communications Officials (APCO) assigns 10-99 the meaning “wanted or stolen.” In practice, the code comes up when a dispatcher runs a license plate, vehicle identification number, or a person’s name through a law enforcement database and the results show an active warrant, a stolen vehicle report, or another flag. The officer hears “10-99” and knows the subject has a record that demands heightened attention.
How Officers Use It on a Stop
Under the common APCO-based meaning, 10-99 typically surfaces during a traffic stop or field contact. An officer calls in a plate number or a subject’s identifying information. The dispatcher runs it through databases like the National Crime Information Center (NCIC). If the check comes back with a hit, the dispatcher transmits 10-99 to alert the officer that the person or vehicle is flagged as wanted or stolen.
That single transmission changes the encounter immediately. An officer who was writing a routine citation is now dealing with a potentially dangerous situation. Backup may be requested, and the officer’s approach to the subject shifts. In departments where 10-99 carries this meaning, it is one of the codes officers take most seriously, because it tells them the person in front of them may have an active warrant or be connected to a stolen vehicle.
Other Meanings You May Encounter
Plenty of agencies never adopted the APCO definition. The NYPD uses 10-99 as an administrative disposition code meaning “other final disposition,” essentially a catch-all for closing out a radio call that does not fit other categories. At least one department’s code chart lists 10-99 as “warrant process,” referring to serving or processing a warrant rather than flagging a database hit. A widely circulated older code list attributes 10-99 to something as mundane as “open police garage door.”
The California Highway Patrol does not use 10-99 at all for emergencies. CHP runs an entirely separate numbering system in which 11-99 means “officer needs emergency help,” a code that occasionally gets confused with 10-99 in popular culture and online discussions.
Where 10-99 is purely administrative, hearing it on the radio does not change anyone’s behavior. Where it flags a wanted or stolen hit, it changes everything. Same three digits, different worlds.
Why the Same Code Means Different Things
The original APCO ten-signals were developed in 1937 by Charles Hopper, communications director for the Illinois State Police, to cut down on radio chatter when channel space was scarce. APCO published a standardized list, but adoption was always voluntary. Individual departments modified codes to fit their own needs, added new ones, and sometimes reassigned meanings entirely. Over decades, this produced a patchwork where the same number could trigger completely different responses depending on which side of a county line you were on.
The Department of Justice has noted that 10-codes “vary across jurisdictions” and “can potentially confuse first responders from different agencies when they work together.”1Office of Justice Programs. 10-4 No More? Law Enforcement Agencies Are Phasing Out Old Radio Codes When officers from neighboring jurisdictions respond to the same incident and one agency’s 10-99 means “wanted person confirmed” while another’s means “open the garage,” the potential for dangerous miscommunication is real.
The Shift Toward Plain Language
Since fiscal year 2006, the Department of Homeland Security has required plain language during multi-agency, multi-jurisdiction incidents as a condition of federal preparedness grant funding, through the National Incident Management System (NIMS).2Federal Emergency Management Agency (FEMA). NIMS Alert – Plain Language NIMS does not require plain language for a department’s internal day-to-day operations, but it encourages the practice so officers are comfortable using it when a large-scale emergency hits.
Under NIMS, plain language means common terms that responders from any discipline can understand without a decoder. Instead of transmitting “10-99,” an officer would say “plate comes back stolen” or “subject has an active warrant.” Slower to say, harder to misinterpret. Maryland fully eliminated 10-codes, and at the last major survey, at least nineteen states had planned to follow. Many departments that still allow 10-codes internally switch to plain language whenever they are working alongside other agencies.3Police1. Police 10 Codes vs Plain Language The History and Ongoing Debate
If You Hear 10-99 on a Scanner
Most people encounter 10-codes through police scanner apps or online streaming platforms that broadcast live radio traffic. These apps sometimes include built-in code charts, but those charts almost always reflect a single version of the codes, usually the APCO standard or a generic list that may not match the department you are actually listening to. If you hear “10-99” on a scanner stream from your local department, the only way to know what it means is to find that specific department’s code list, assuming it is publicly available.
No single definition of 10-99 is universally correct. The APCO expanded list says “wanted or stolen,” and that is the most widely referenced meaning, but your local department may use it differently or may not use 10-codes at all. As more agencies complete the transition to plain language, the practical relevance of any specific 10-code continues to shrink.