Homicides in Boston are on track to fall for the third straight year, driven downward by solid police work, an aging population, and better trauma care, according to law enforcement officials and specialists.

Jack Levin, professor of sociology and criminology at Northeastern University, credited the drop in homicides in Boston to police work, a high number of immigrants, and a population that is aging.

When the number of killings peaked in Boston in 1990 at 152, the city began employing new methods that helped cut into the homicide rate, Levin said.