The fraught relationship between Baltimore State's Attorney Marilyn J. Mosby and the city police seemed to ease a bit the other day with the announcement of a new joint effort to end violence. The idea is to team up under one roof a new unit focused on bringing to justice “those who are administering gun violence in the city,” as Ms. Mosby politely put it.

But does she know what that will take? I have doubts. Let's go to court to see what I mean.

On the fourth floor of Courthouse East, Baltimore Circuit Judge Charles Peters presides over a tiny courtroom, where “reception court” is underway for the criminal docket. This is the first stop for prosecutors, defense attorneys, police officers, defendants and family members, who cram the few pews each business day on the slim possibility that their case will actually go to trial.

Judge Peters calls the docket. After conferring with the lawyers on either side of a given case, he usually grants a postponement. Much less frequently, he finds an open courtroom and directs the parties there. Occasionally, the defendant is ready to plead guilty immediately, in exchange for a reduced sentence as part of a deal struck with prosecutors. When I was there a couple of months ago, I happened to witness such an outcome.

The defendant was led in, wearing a yellow jumpsuit, handcuffs and shackles. When all the boilerplate was read into the court record, the defendant left the courtroom with the following sentence: for drug distribution, 10 years, all but 18 months suspended; for “handgun in the possession of a prohibited person,” one year, to run concurrently with the 18 months.

Thus a man with a prior felony conviction, caught selling drugs and packing a gun, got a year and a half of incarceration, with credit for time already served prior to his plea. He could expect to go home within a few months. There was nothing remarkable about this outcome. It happens all the time in Baltimore City.

Ms. Mosby wants to target the 602 persons she blames for most of the daily shootings — more than 175 of them fatal since the beginning of 2016 — that afflict our city and inure us to violence. “We know who the trigger pullers are,” she said, calling them “violent repeat offenders.”

Our city has many of those, yes, but Ms. Mosby should keep in mind that you don't go from being late for choir practice to being John Dillinger overnight. You get to learn your craft because the courts keep returning the vast majority of gun offenders to the street — usually with the blessing of the state's attorney's office, which is staffed by heavily overworked and increasingly inexperienced prosecutors. (The brain drain in the state's attorney's office since the beginning of 2015 has reached crisis proportions, by many accounts.) Judges are also are only too happy to comply; they have to clear their dockets, and the zeitgeist counsels against sending too many people to prison.

The Sun's Kevin Rector provided a useful analysis on July 24 of this year, using figures provided by Baltimore Police Commissioner Kevin Davis. As of that date, 822 people had been arrested for gun possession in the city (it would be nice to know how many of them had made bail), and court cases for 149 of them had worked their way through the system. Of those, 52 people had been found guilty, six were acquitted and the charges against 91 defendants — more than half of the adjudicated cases — were dropped. The 52 people found guilty of illegal gun possession were sentenced to a grand total of 65 real-time, unsuspended, years in prison.

As Mr. Davis noted during the news conference to announce the new gun unit, illegal possession of a firearm is still, shamefully, a misdemeanor in Maryland. But make no mistake, he said: A gun arrest “is a pre-murder arrest.” (Let's note here that 90 percent of last year's 344 Baltimore City homicides were accomplished with a firearm.)

A sergeant and four full-time detectives will be assigned to work with a new “elite” unit of prosecutors to go after the most savage gun offenders, as identified by various criminal intelligence sources. But will the new Gun Violence Enforcement Division have discretion to go after rookie gun offenders as well, before they graduate to mayhem and murder? Will Ms. Mosby revise her in-house directives to prosecutors to work out sweetheart plea agreements whenever possible? Will she consider calling out judges who consistently undercut serious sentencing recommendations?

Or will she wait until a shooter joins the Savage 600 to attempt to take him off the street for real?

Hal Riedl retired from the Maryland Division of Correction in 2010 and from the office of the state's attorney for Baltimore City in December 2014. His email is haroldriedl@gmail.com.