It has come to this: The people whose word prosecutors ask jurors to believe every day to put criminals behind bars cannot be trusted not to lie on their weekly time sheets and so now must scan their fingerprints and the start and end of their shifts.

It’s not that we disagree with the Baltimore Police Department’s decision to invest in technology to help prevent fraudulent overtime. Police departments will always need to spend some amount on overtime as they cope with unforeseeable circumstances. But spending nearly a million dollars a week on overtime while still struggling to put enough men and women in uniform on the street is unsustainable; we can’t afford to pay for even a single hour of overtime that isn’t justified. And the trial of two former members of the department’s Gun Trace Task Force has revealed that overtime fraud in the department isn’t just a problem, it’s routine. Testimony in the case revealed that it was common practice for some supervisors to sign off on falsified time sheets with few questions asked, and subsequent reporting by The Sun’s Kevin Rector shows that many saw nothing wrong with it. Pervasive informal policies in the department allowed officers to get paid time off for doing what their commanders perceived to be a good job. Officers got “g days” for seizing guns or “slash days” for good performance. Paying unearned overtime was considered a standard management tool for front-line supervisors, according to testimony in the trial and Mr. Rector’s interviews with current and former commanders.

That, in its way, is more damaging than the outrageous corruption to which several former Gun Trace Task Force members have pleaded guilty. The task force can be written off as a rogue group that operated by its own rules and avoided any kind of meaningful oversight — until federal investigators caught wind of their activities, that is. The more mundane time sheet fraud Mr. Rector described, by contrast, reinforces the idea that Baltimore police can’t be trusted to play by the book. And it’s not the only recent piece of evidence for that belief.

There is the officer who is now charged with misconduct and fabricating evidence after body camera video showed him placing drugs in a trash-strewn alley and then “finding” them moments later. Even his defense — that he was merely recreating an earlier discovery of the drugs — is an admission of not following the rules. Or there is the officer who claimed on the witness stand to have seen a defendant on a particular block nearly every day for 18 months, despite the fact that the man was in prison most of that time. The officer remained on the job anyway.

In that context, it’s harder to dismiss as isolated incidents some of the outrages we’ve learned about during the Gun Trace Task Force trial. Between officers pretending to be federal agents, conducting warrantless searches, carrying BB guns to plant on people, stealing money and drugs, lying about how much cash they seized in raids, and on and on, you begin to get a sense of the magnitude of the problem Baltimore’s new police commissioner, Darryl De Sousa, faces in the effort to rebuild the public’s faith in the department.

Police spokesman T.J. Smith said the new fingerprint scanners aren’t a sign that commanders don’t trust the cops but are a means to show the public that the department is doing something about a system that’s susceptible to abuse. But what the public sees is not a faulty system but a faulty organizational culture. It’s going to take a lot more than a few fancy time clocks to fix that.