Last week, Suffolk County District Attorney candidate Greg Henning broke a taboo of sorts. Henning, on leave from his job under current DA Dan Conley, proposed a new unit in that office dedicated to solving and prosecuting non-fatal shootings — conceding, by implication, that Boston law enforcement doesn’t currently do as much as it could to arrest those who fire weapons in the city.

That’s an admission stubbornly resisted by Conley, by outgoing Boston Police Department Commissioner Bill Evans, and by Mayor Marty Walsh. They have all publicly insisted that Boston’s low arrest rate for non-fatal shootings is due entirely from lack of co-operation, and that there is nothing the BPD could do differently to improve the results.

“The ones that we can solve, we do solve,” as Evans put it in a 2017 WGBH radio interview.

Henning, currently supervisor of the DA office’s gang unit, and previously head of its gun prosecution task force (which primarily handles gun possession cases), proposes a five-person unit. Three hand-picked prosecutors, a data analyst, and a victim advocate would “quarterback investigations” of shootings that result in non-fatal injuries, or no injuries at all, Henning says.

That might include subpoenaing records, getting grand jury testimony, gathering information and materials from other agencies — say, video from MBTA security cameras — and cross-referencing with information on other crimes under investigation.

In other words, getting more involved in actually investigating and solving the crimes, rather than merely prosecuting once the police make an arrest.

In theory, that could close some of the enormous current gap between the investigation of fatal shootings and non-fatal ones. A dedicated homicide unit in the DA office works with an elite, centralized detective unit within the Boston Police Department, or with the State Police for murders elsewhere in the county. Non-fatal shootings are investigated by detectives at BPD’s districts, and by the local Chelsea, Revere, and Winthrop police departments.

Mostly, of course, that takes place in a small number of Boston districts where the bulk of the area’s roughly 250 official shootings occur each year. Very few are ever solved.

Henning says that by his tally, there are actually more than 700 calls for shots fired in Boston each year. That’s a big stream of cases for his proposed five-person unit to tackle, but Henning says the team could be expanded if it proves successful.

“If you can solve a percentage of them,” Henning says, “You take that brazen shooter off the streets. That can prevent future shootings.”

His opponents in the DA race agree on the importance of increasing that arrest rate. Unsurprisingly, they deride him for proposing the idea only now, during his campaign.

“I think the timing is awfully convenient,” says Rachel Rollins. “Greg has been in the DA’s office for 10 years, and never thought to do this?”

“It’s disingenuous of Greg, who has been in the gang unit to never raise this issue in his time there,” says Linda Champion.

“I think that’s deeply concerning, to be just coming to this conclusion now,” says Shannon McAuliffe, who adds that Henning’s plan says nothing about transparency, benchmarks, and measurements that would show whether the unit is having any effect.

The four other Democratic candidates seem to accept Henning’s implicit premise that the DA’s office has a role in improving the arrest rate for shootings. Their notions of how to accomplish that, however, are mostly limited to improving community trust in hopes of gaining more cooperation from witnesses.

“Until the DA’s office can prove with certainty that they can protect the witnesses, they will continue to face a wall of silence,” says Champion.

That’s an admirable goal, and one that in theory the DA office can help with. It controls funds and services for witness protections, even up to moving families for their safety.

Realistically, though, those resources are already stretched too thin, and are needed for cases against murderers. It’s hard to imagine any DA finding much in that budget to spare on non-fatal shooting cases.

McAuliffe, who has seen the problem from the perspective of a defense attorney, argues that a cultural change is also needed. Too often, she says, prosecutors treat victims—often the most important potential witness in a non-fatal shooting case—like just another criminal who could have just as easily been the shooter, or will be next time. “The DA’s office has been more interested in judging them, and complaining about their non-cooperation,” she says.

No doubt, cooperation from witnesses is a major impediment to solving shootings. That’s true in every city, of course, but there are reasons to think the problem might be a little worse in Boston than elsewhere, both because of its densely populated black neighborhoods and its long history of racial distrust.

Still, concrete examples are scarce for how to improve that situation, and gain more trust from legitimately fearful residents.

Meanwhile, none of the DA candidates — and certainly not new Commissioner William Gross, or Walsh — are willing to suggest that the BPD might need to actually improve its investigative procedures, protocols, personnel, training, or operations.

When I asked Henning, for example, whether he would like the new BPD commissioner to consider creating a centralized, dedicated shootings investigation unit to mirror the one he hopes to have at the DA office, he would only say that he looks forward to working with Gross, and having a conversation with him after he takes office about what they can do working together on the issue. (The BPD did not respond to requests to interview Gross or others for this article.)

The truth is, the best thing the next DA could do to improve the shootings arrest rate might be to pressure the BPD to actually address a problem that it only acknowledges internally.

Several years ago, the department proposed a study of how different protocols might improve what it described as unacceptably low clearance rates for non-fatal shootings — a proposal similar to one it conducted at the time for homicide investigations. That homicide study purported, in a report last year, to improve the arrest rate, while identifying specific improvements.

Its conclusion: enhanced investigative resources, a “comprehensive resource mindset,” and problem-oriented policing leads to more solved homicides.

The study of non-fatal shooting investigations, by contrast, never took place.

A 2015 outside audit of the department, ordered by Walsh along with reviews of other city departments, raised questions about the deployment, oversight, and workload of the detectives who investigate these non-fatal shootings. The report also found concerns that “communication between districts, specialized unit detectives, and district detectives needed improvements in order to increase the effectiveness of operations.”

There was no follow-up or changes made based on those findings.

Instead, BPD and city officials — and the DA’s office — rely on the word of Boston’s detectives that they have no room for improvement.

That might seem strange. But, the authors of that BPD homicide study actually addressed that problem, in a final section added to the final report issued a year ago.

“In reforming investigative practices and processes, police executives will be forced to confront the powerful culture of detectives and the mythology that surrounds their work,” wrote Anthony Braga of Northeastern University and Desiree Dusseault, deputy chief of staff to then-commissioner Evans. “The process will take considerable political will and persistence by the chief executive and other key personnel in the department.”

Henning’s proposal, while not a cure-all, suggests that the political will might come from the DA office—thanks to the rare opportunity of a campaign for the open job.

The candidates say that shootings — and low arrest rates — are high on residents’ minds on the hustings. That’s leading Henning and the others to promise improvements, which the winner will feel politically pressured to deliver on. That will require help from the BPD.

At the very least, it has forced the next DA, whoever that turns out to be, to acknowledge that the status quo is not good enough. That’s a start.