There are people who’ve gotten away with murder in Rhode Island. The graves of their victims have long been covered, and the trails to the killers have grown cold.

Now, Providence police Col. Dean M. Esserman wants to organize a cold-case homicide unit by January – with an eye to taking on unsolved murders from all over the state.

More than a third of homicide cases go unsolved nationally; last year, the clearance rate was 62 percent nationwide, meaning the police charged someone with murder. Providence’s clearance rate was 55 percent last year; the police have made arrests in 4 out of 10 homicides this year.

Esserman said the department was tallying its unsolved homicide cases going back decades. “I think about all of them. I know what it means to the families,” he said.

The idea for a cold-case unit has been on his mind for two years, Esserman said, but over the last several months, he’s begun putting the plan into works. He’s getting advice from his former deputy chief, Andrew Rosenzweig, a veteran with 40 years in law enforcement whose work solving a 30-year-old double murder in New York was chronicled in a critically acclaimed book A Cold Case.

Rosenzweig, now director of Cold Case Forum, a Newport business that trains and offers consulting services on solving old homicide cases, called the national rate of unsolved murders “close to a crisis.” “There’s thousands upon thousands of people who’ve evaded justice, and that many families who’ve not had even that small amount of comfort that their loved one’s killer was brought to justice,” he said yesterday.

There are reasons that homicide cases stall – the lack of witnesses, physical evidence, or police resources to continue investigations, Rosenzweig said. But for those who loved the murder victim, time doesn’t aid the agony waiting for the killer to be caught.

“In this work, it’s tenacity, tenacity, tenacity,” Rosenzweig said. “You have to stay with the case and be passionate about it, and never forget the victims.”

Esserman envisions a cold-case unit of current and retired detectives, as well as medical and mental-health doctors, whose expertise could aid the investigators when they begin knocking on the doors of people waiting for answers in their loved one’s murder. “Some people are just waiting for that call to open up the case,” Esserman said.

The cost and size of the unit, and whether it will investigate homicides locally or across Rhode Island, are questions that have yet to be answered. Esserman raised the idea with Attorney General Patrick C. Lynch and Mayor David N. Cicilline.

The cold-case unit is similar to the homicide task force at the attorney general’s office, which solved a 1990 North Providence murder two years ago and is investigating others. Lynch said he thinks it’s a good idea to have a formal cold case unit, even starting with a prototype in Providence County, which has the most homicide cases. “It’s certainly something we can take statewide,” he said.

Esserman is holding meetings with law enforcement officials and investigators from across the state to figure out how the unit will function.

“If we’re not looking back, these people that commit these heinous crimes don’t reform all of a sudden. We could surmise they’re still committing crimes, they’re still causing mayhem,” Rosenzweig said. “I think it’s a mistake to stop looking back. It’s not just about taking this old case off the shelf. It’s about what are they doing now.”