Barrett, who is from San Diego and whose father was a police officer, said the 10-codes, also called "brevity codes," were never designed to relay all the information needed. "You always had to follow up with more details," he said.
Lookouts for Baltimore drug dealers still call out "Five-O" when police are spotted — a reference to the show "Hawaii Five-O." Barrett said that, no matter what happens to the official lingo, "'10-4' and 'What's your 20?' will always be with us. They're too ingrained in our lingo."
Montgomery County Police Sgt. Alan Felson, who helped implement plain language in the suburban Washington department in 2006, agreed. "The codes are the way police talk," he said. "Taking them away is taking away a part of police culture."
Felson said that since the Sept. 11 terrorist attacks, there has been a concerted push to ensure police and firefighters can talk to each other.
"We've invested millions of dollars on the technical end, saying we want a common system with which to communicate," said Felson, noting that improved, common radio bands used by police spread across vast areas.
"That investment would be largely wasted if one officer in one place doesn't understand what an officer from another place is saying," Felson said. "We have compatible radios. We need to have compatible speech."
Retired Baltimore police Lt. Col. Michael J. Andrew, who joined the force in 1973, said police officers may recall the most basic and oft-used codes, but he said "other ones haven't been used for years" and that "officers use plain language most of the time."
Codes used most often, such as "10-7," meaning "out of service," have evolved on their own. On the city streets, it applies equally to relay that a cop is on a bathroom break, his car has broken down, or a person who was just shot has died.
And the codes have grown more intricate and detailed. An Anne Arundel County officer seeking the time asks for a "10-36." Baltimore County adds lettered labels to its codes to differentiate between different kinds of gambling and 19 different kinds of accidents. A cop in Prince George's County who wants to know the weather asks for a "10-13."
Andrew, the retired Baltimore police commander, said that "most codes haven't been used by officers for years." He said that if a dispatcher shouted over the air "10-51" — a helicopter crash — "I bet there's a significant number of officers who wouldn't know what was going on."