His face flushed under the shining sun, Bruce McArthur stands before the Niagara Falls, a rainbow rising into the azure sky from the mist behind him.

Dishevelled and his eyes bloodshot, Dean Lisowick stares with a weary expression from a police mug shot snapped in front of a grey background.

It has been more than three weeks since Toronto police took Mr. McArthur into custody and the pictures of the 66-year-old landscaper and the five men he is accused of murdering have now became stamped in the public consciousness.

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The criminal charges against Mr. McArthur still have to be tested in court, but one recurring talking point has been the disparity between the images of the accused and the five slain men.

In one widely republished picture, Mr. McArthur poses in front of Niagara Falls. In contrast, Mr. Lisowick, one of the five men police identified as victims, is mostly known for his forlorn-looking mug shot from a past brush with the law.

"I'm really struck by … these avuncular shots of him, the dignity being afforded to Mr. McArthur and not to the others," said Nicki Ward, a director of the Church-Wellesley Neighbourhood Association.

Toronto police didn't make public a mug shot of Mr. McArthur after he was apprehended on Jan. 18.

Officers were following standard procedure. Typically, Toronto police will only release mug shots if they are seeking a fugitive or if investigators are making an appeal to the public to see if more potential victims could step forward – for example, in investigations of serial fraudsters or sex predators.

"We have a high threshold for us to release a picture. There has to be a valid investigative purpose," Toronto police spokesman Mark Pugash said.

However, within minutes of the news of Mr. McArthur's arrest, his Facebook page was already being shared online and media outlets harvested pictures from that social-media account and from his online dating profiles.

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The public image of Mr. McArthur thus became the visual profile that he had chosen to define for himself, mostly with flattering pictures that he had curated before his arrest.

The slain men, meanwhile, had fainter digital footprints. Those who had Facebook accounts had posted few public pictures. Worse, in the case of Mr. Lisowick, he was homeless, so the first available picture was a police-released past mug shot.

Years ago, reporters who needed pictures of crime victims had to do "pick-ups," the practice of tracking down relatives of a dead person and persuading them to share their photo albums, said Jeffrey Dvorkin, director of the journalism program at the University of Toronto Scarborough.

With fewer resources and tighter deadlines, media outlets search first for photos online these days. As a result, the visuals for Mr. McArthur are abundant and readily accessible but they are, Prof. Dvorkin noted, "de-contextualized information."

The public's expectation may also be skewed by exposure to mass media from the United States, a country where mug shots are widely accessible, he said.

Mug shot rules vary widely from country to country. In France, the law forbids the publication of images of suspects in handcuffs or in custody until they have been convicted. In the United States, however, most jurisdictions consider booking pictures public records. This has spawned a cottage industry of websites that put mug shots online and related "reputation management" firms that charge a fee to remove those pictures.

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Anthony Morgan, a Toronto lawyer with an interest in anti-racism issues, said the imbalance in the way Mr. McArthur and Mr. Lisowick are portrayed has parallels with the way negative images of blacks and native people are perpetuated.

While the police might say that their approach is neutral, it is problematic if it reinforces existing biases, he said.

"There has to be a consideration, a due diligence, applying social analysis to what would be the impact on the community," Mr. Morgan said.

At a vigil for the five men held a week ago, Ms. Ward ran into someone who was carrying a blown-up picture of Mr. Lisowick.

"Please, please, can I take a photograph of it?" she asked.

She has since shared her snapshot of that picture with several media outlets so his mug shot doesn't have to be circulated any more.