
What Does J4 Mean in Police Code? Why Context Matters
J4 can mean fatality in some police code systems, but it is not universal. Learn why the agency…

There is no universal U.S. police meaning for code 304. If you found a website saying “304 means vehicle hijacking” without naming the department, treat that answer cautiously.
Published code lists show exactly why. A police-code database lists 304 as “investigate car blocking” for New Britain, Connecticut and “traffic unit” for Niagara Falls, New York. Other coding systems use 304 differently again.
Because many police codes are local. Departments developed their own signals and adapted older systems to fit local dispatch needs. A three-digit code is not automatically part of a nationwide standard.
You will see that claim online, including on ProudPolice. I could not verify it as a nationwide police-code meaning, and other published agency examples conflict with it. The safer answer is that 304 can mean different things depending on the agency.
Identify the department or dispatch center first. Then look for that agency’s own radio-code list, policy manual or communications documentation. A generic code website should be a fallback, not the first authority.
Our broader police radio codes guide explains why this problem is so common.
“304 police code” does not have one reliable national translation. The agency and jurisdiction are part of the answer.

J4 can mean fatality in some police code systems, but it is not universal. Learn why the agency…

Police code 519 can mean an injury accident in some systems, but police codes vary by agency. Here…

Police radio codes are not universal. Learn how 10-codes, local signals and plain language work—and why the same…