This story is part of the Star’s trust initiative, where, every week, we take readers behind the scenes of our journalism. This week, we focus on how the Star vetted and presented explosive photographs that exposed murder and torture at the hands of an elite unit known as the Iraqi Emergency Response Division (ERD) fighting Daesh (also known as ISIS).

“Really need to stop looking through these as I know you all must feel, too,” writes National Security reporter Michelle Shephard in an April 11 email to a small team of reporters and editors. At the time, the group was in the midst of going through more than 450 photographs and videos depicting acts of torture — gagged and blindfolded Iraqi detainees being slung from ceilings by their wrists, or with live wires put to their heads. Videos of men screaming their innocence while being beaten; and in one case shot dead.

“For me, something about (photograph) 168.jpg or 169.jpg is really haunting … the dangling cigarette just speaks to the banality of evil,” Shephard adds.

Her email (one of hundreds exchanged among the team over several weeks) was part of a larger discussion about which 20 photographs would portray the most complete story of the unit, called the ERD.

Associate editor Lynn McAuley, who led the investigation, knew publishing too many images could overwhelm. At the same time, she wanted to ensure the Star was fair in its selection. In one email, McAuley writes that she was not comfortable identifying specific members of the unit in photographs unless it was clear those individuals had participated in torture.

“We didn’t take these pictures and just say ‘OK great, let’s put them online,’ ” McAuley says.

The careful curation took weeks ofwork that began with vetting the authenticity of the images and understanding the context and stories behind them.

The photographs were offered to McAuley for publication at the end of March by way of VII Photo, a New York City-based agency that specializes in conflict photography. VII was representing Iraqi photographer, Ali Arkady, as he exposed the abuses he had captured while embedded with the unit. The organization was also trying to get him to safety, hopefully through the Global Reporting Centre at the University of British Columbia. McAuley says she was deeply affected when she first saw the photos, which were also offered to ABC News in New York.

She immediately assembled a team to report.

In addition to Shephard, who has been reporting on terrorism since 9/11, McAuley pulled in foreign affairs writer Mitch Potter and Ottawa bureau chief Bruce Campion-Smith. Both have reported from Iraq.

Potter flew to Europe to meet with Arkady, who had fled there amid death threats (the Star is not revealing his exact location out of safety concerns). There, Potter assessed Arkady’s credibility during 18 hours of interviews that began with his childhood, touched on his history with photography, then went through his time spent embedded with the ERD — a unit Arkady initially thought of as “heroes” in the fight against Daesh before witnessing their brutality.

The pair then went through every one of Arkady’s raw photographs with great detail, identifying individuals involved and the back story. For example, Arkady told Potter the story of a shepherd named Mahdi who is shown in a photograph from November 2016 with his arms strung up behind his back during an interrogation. Mahdi’s son listened to his father’s screams from an adjacent room.

Potter was searching for any red flags that might indicate any of the photographs were staged.

“I asked him a thousand questions and I left with the impression that this guy was real and genuine,” Potter says.

Arkady had also obtained video, including one of an execution at the hands of ERD members. These required an additional level of vetting since Arkady hadn’t shot them himself and wasn’t present. The Star stripped out the audio and sought independent translations.

Arkady also wrote a diary of his time embedded with the ERD. Editor McAuley took this diary and set out to verify every confirmable fact in it. For example, Arkady wrote the ERD headquarters was 100 metres away from another military base, which McAuley confirmed to be true. Using local coverage and wire services, she verified dozens of similar facts.

Shephard consulted at-length with Iraqi researchers for Human Rights Watch, who were part of a small group that knew about Arkady and his images. The researchers had been documenting human rights abuses and war crimes in Iraq and reported that Arkady’s work was, anecdotally at least, consistent with what they were hearing on the ground. Shephard also spoke with photographer, Ed Kashi; a mentor of Arkady’s who verified the sequence of events Arkady had told Potter.

While reporter Campion-Smith’s primary role was to investigate whether Canada ever trained or supported the ERD (they did not directly, though the Canadian government supports the Iraqi government, which is in charge of the ERD) his discussions with officials at Global Affairs and National Defence “did provide a measure of a gut check” when it came to verifying the authenticity of the photographs and videos. Canadian officials looked closely at the photographs Campion-Smith showed them, including at the equipment they had and the uniforms worn. “We looked at the execution video several times,” Campion-Smith says, adding officials noted that the blood mist in the video and the way the man drops would be hard to fake.

“There were no red flags raised during that viewing that caused us to have concern about the authenticity,” Campion-Smith says.

Having done such extensive reporting gave the team the knowledge they needed to select the photographs and videos that would best tell the story of the ERD, and to offer a powerful narrative to accompany them.

Of course, spending such long periods looking at photographs and video of torture and murder was not easy for anyone at the Star.

“On a personal note,” says Shephard, “Over the years I’ve had to look at hundreds of videos, photos or have witnessed myself the war crimes committed by terrorists and governments, and what made this so fundamentally depressing and poignant was the fact that (Arkady’s) work uncovered how terrorism is being fought with terror, which just means the cycle will never end.”