Charles E. Rinaldi, a retired assistant chief of the D.C. police who was an early advocate of the “broken windows” theory of police work and helped cut crime in a troubled part of the city in the 1970s, died July 20 at Frederick Memorial Hospital. He was 84.

The cause was pneumonia, a complication from surgery, said his daughter Victoria Rinaldi Alten.

Mr. Rinaldi served in the D.C. police department for three decades, having joined the force in 1954 and risen through the ranks as a police officer and detective. In 1976, he was promoted to head the 3rd District. The territory included 14th Street NW, Logan Circle and Thomas Circle and was notorious for its high incidence of prostitution, drug use and street robberies.

Under Mr. Rinaldi, the 3rd District five times won a department-wide award for cutting crime rates. His success helped propel him in 1979 to the post of assistant police chief for technical services, which included the police laboratory and department communications. That position, in turn, put him on the short list of candidates to replace Burtell M. Jefferson, the first African American D.C. police chief, when he retired in 1981.

Sen. Alfonse M. D’Amato (R-N.Y.), as chairman of the D.C. appropriations subcommittee, took the unusual step of endorsing Mr. Rinaldi for the job. In a letter to then-Mayor Marion Barry (D), D’Amato cited what he described as Mr. Rinaldi’s “broad” community support, his “impeccable” professional credentials and his long experience.

However, many people believed at the time in the importance of appointing an African American person to be Jefferson’s successor. D’Amato’s proposal also encountered resistance from those who resented federal influence on local decision-making.

Barry selected Maurice T. Turner Jr., a veteran African American police officer who was then assistant chief in charge of field operations. Mr. Rinaldi remained with the force as assistant chief for technical services until his retirement in 1984.

In the 3rd District, Mr. Rinaldi had worked to create what he called a police “aura of omnipresence.” He reestablished beats for officers patrolling on foot and on scooters so that the police would be more visible to residents.

In what seemed to be an early application in Washington of what became known as the broken windows theory of crime suppression, he also ordered officers to strictly enforce traffic and littering laws. The idea was that quickly responding to relatively minor transgressions would deter the commission of more serious offenses.

He was particularly concerned with sex trafficking, a matter that many preferred to ignore.

“If you get the prostitutes,” Mr. Rinaldi told The Washington Post, “they are the rats. Get rid of them and the other vermin that accompany them also leave the area.”

Charles Edward Rinaldi was born July 7, 1928, in the District, the son of Sicilian immigrants. He was a 1947 graduate of Roosevelt High School.

Mr. Rinaldi was studying pharmacology at the University of Maryland when his Army National Guard unit was activated during the Korean War. He served in Korea as a medic and then as a military police officer.

After his military service, he studied law enforcement at George Washington University but left college to enter the police academy.

“It shocked my mother,” he once told The Post. “I distinctly remember that she dropped her coffee cup.”

His son, Charles W. Rinaldi, died in 2006. Survivors include his wife of 57 years, JoAnn Ruddle Rinaldi of Adamstown; two daughters, Victoria Rinaldi Alten of Cornwallville, N.Y., and Elizabeth Rinaldi Burdick of Barnesville; and three grandchildren.