At the beginning of the year, we asked ProPublica Illinois readers what they wanted to know about how we do our work. The questions have been rolling in ever since, and we’ve been answering them in an occasional series of columns. Today, ProPublica Illinois reporter Jason Grotto answers an inquiry about how we deal with the potential for bias in reporting.

What steps does ProPublica have in place in the editorial process to reduce and control bias? — Scott Dyson

The truth is, journalism has long struggled with the idea of bias and, through many periods since the founding of the Republic, much of the press has sometimes been openly partisan. “Objectivity,” relatively speaking, is a more recent cultural standard. So, I look at the idea of bias as part of a lengthy and ongoing conversation, one I hope will never end.

First, it’s important to point out that ProPublica focuses mainly on investigative journalism, which is a particular genre that makes its reporting different than, say, political coverage. In most cases, investigative stories make an argument rather than just capture both sides of an issue. The stories often have a particular structure: Some person, government agency or other entity allegedly did something wrong and harmed others. Almost always, the wrongdoing is set against a standard — a law, ethical practice or norm.

So on a certain level, some point of view is baked into investigative stories because, in many cases, reporters begin with a tip or data that suggests wrongdoing and then set out to determine if it occurred.

When a colleague and I exposed how Chicago Public Schools lost more than $100 million using high-risk borrowing to fund school construction projects, we worked from the premise that school officials should be prudent with education funding.

Before we embark on a story, there is a long process of vetting the idea. Reporters often write pitch memos that give broad outlines of what might be uncovered, after doing some spadework. In doing so, both reporters and editors make sure multiple viewpoints are sought.

In the reporting, we have to be sure the question we pursue can be answered with verifiable facts. The key is “verifiable.” That is, any fact presented in a story must be based on documents, data or reliable, on-the-record human sources.

When I was a reporter at the Chicago Tribune, I did a series of stories about union officials who violated state law by double- or even triple-dipping on pension payouts, collecting money from both public and union pensions for the same work. The investigation launched after we got a tip. We nailed down the story by digging through years’ worth of documents from public pension funds and union records filed with the U.S. Department of Labor.

By lining up the two sets of records, we showed union officials flouted state law by collecting two pensions for the same work. That contributed to the underfunding of public pension funds union members relied on for retirement.

As I dug through records and did interviews, I looked for evidence that knocked down or mitigated our premise. Every reporter should seek out facts that might produce a counternarrative. You don’t want to have tunnel vision.

The idea is to ensure fairness and accuracy, the twin pillars of high-quality journalism.

One thing I love about our shop at ProPublica is that we go out of our way to provide source documents, as we did with our work on sexual assault allegations at the Red Cross. If we do a large data analysis, we often provide detailed methodologies along with the data so readers can delve into the evidence we present. A great example of this is ProPublica’s recent series on bankruptcies.

Because every fact in every story springs from verifiable information, journalists are obsessed with fact-checking their stories, which is another way we ensure accuracy. This process entails going back over every fact in a story and re-checking primary source information before publication. You can’t have fairness without accuracy.

You also can’t have accuracy without fairness, and that brings us to another important part of the process: what I refer to as layered editing. Any significant news story you encounter in a top-flight operation has been reviewed by multiple editors. Each editor searches for claims in the story that aren’t backed up and pokes at leaps of logic that aren’t buttoned down.

When I worked at the Miami Herald, I had an editor who used to call us into her office to go over findings in a story. We used to say that we were “going into the box,” a reference to the great, old cop show “Homicide: Life on the Street,” because it was like being interrogated. Reporters love that level of scrutiny before publication. It helps you sleep better.

Here at ProPublica, we often partner with other news outlets, which means reporters not only have three or four editors from our group combing through our work but also editors from our partner publications.

I have a mantra for another way we make sure to tease out any kind of slant that may not be accurate or fair: no surprises. By that I mean, anyone mentioned in the story should know before publication what the story will say and have a chance to respond — not only to specific facts but also to how the story is framed.

Subjects of an investigation should be given every opportunity to challenge both the premise and the facts. That doesn’t mean you put whatever they say into a story. Their responses need to be verified and fact-checked, too.

I recently wrote a series of stories about the Cook County property tax assessment system. The series showed that the office of Cook County Assessor Joseph Berrios, one of the state’s most powerful politicians, knowingly produced flawed assessments that caused lower-income homeowners to pay disproportionately more in property taxes than wealthy ones.

Before we published the series’ first three parts, we sat down with Berrios’ staff for a lengthy and detailed interview. We went through the major points in the drafts of the stories and gave the assessor’s staff the opportunity to push back on our findings. After those first stories ran, the office declined to make officials available for an interview.

As we prepared the fourth part of the series, we sent the assessor’s office a note outlining our main points and asking for another interview. Berrios and his staffers refused, sending along a prepared response. We wrote another letter, this one laying out in greater detail what our reporting had found, and what we planned to publish. We even used language from a draft of the story to make sure they understood the story’s tone. That ensured they had every opportunity to respond.

This part of the reporting process is so important that investigative journalists sometimes send subjects certified letters to ensure they understand what’s coming and have a chance to respond.

Of course, we also rely on readers to keep us honest. It’s why we work hard to engage with you and solicit feedback. If we cross a line, or violate our standards, we have every hope that you’ll call us on it.