Fiona Mowat examines shreds of torn-up clothing, trying to match them to a missing person. She also goes through sketches of unidentified people, hoping to find a familiar face. Sometimes she'll look at a dead body if it means a chance at solving a mystery. 

And she does it all free-of-charge from the computer in her Toronto home.

Mowat is part of an online community of amateur detectives. She and thousands of others spend their free time flipping through police reports, watching closed-circuit television (CCTV)  footage and braving government databases of unidentified remains, trying to answer the most fundamental question surrounding every crime: "What happened?"

As a member of Websleuths.com, a forum that boasts up to 5,000 daily users, she posts her clues and theories about missing people and unsolved murders from across the world.

She got hooked the way many do — searching online for information about a missing person and, by chance, clicking into the world of stay-at-home sleuths who compile everything they can about mysterious crimes. Since joining in 2009, Mowat has spent at least an hour or two a day on her hobby, having made more than 6,000 posts to the website.

"This feels like a job. Obviously it doesn’t pay or anything like that," says Mowat, who freelances occasionally but no longer works full time. "I've worked in all kinds of jobs, and web sleuthing gives me an opportunity to use some of the skills from things I’ve done, and be useful."

From Jeffery ​Boucher to Madeleine ​McCann

Her dedication comes from her desire to help people like Jeffery Boucher, a teacher from Whitby, Ont. reported missing on Jan. 13.

BRITAIN

A high-profile mystery like the disappearance of Madeleine McCann can generate hundreds of topic threads and hundreds of thousands of page views on online detective sites like Websleuths.com. (David Moir/Reuters)

The Websleuths topic thread on Boucher has more than 1,000 replies and over 60,000 views. Larger mysteries, like the disappearance of three-year-old Madeleine McCann, can generate hundreds of topic threads and more than one million views.

McCann, a U.K. girl who disappeared during a 2007 family vacation in Portugal, has captivated people like Anya Chand for more than six years.

The London, England-based writer started following the McCann case soon after she disappeared. Chand, a 43-year-old parent of one, says she follows the case out of curiosity — curiosity strong enough to spend months reading 11,000 pages of case files.

'We're all afraid that something like this might happen to us.'- Sleuth Anya Chand on McCann's disappearance 

What internet investigators lack in tools and training, they make up for in sheer numbers. In December, five people disappeared when their plane crashed into a snowy Idaho mountainside. After official searches were suspended, family members made a personal appeal to the forum, asking users to search for the wreck through satellite images.

The full-time writer and Websleuths member recently finished a novel about a missing girl. Her story, Aida Was Here, features some parallels to Madeleine’s disappearance, but isn’t based on the case, she says, citing at least one key difference.

"My girl was found," she says.

What motivates a sleuth? 

Success is difficult to define for an internet sleuth. Police detectives aim to arrest criminals, but online detectives don't have that power — or access to forensic tools, or the ability to interview and interrogate people. So what pushes people to pursue these cases?

Anya Chand Hands

Websleuths.com has 67,000 registered users, and between 2,000 and 5,000 active users per day, says website co-owner Tricia Griffith. (Jesse Tahirali/CBC)

Many are thinking of the victims' relatives, says Tricia Griffith, co-owner of Websleuths. She says even if police have stopped investigating, some good comes out of keeping cold cases alive.

"Just knowing that somebody else cares means a great deal to the families," she says.

And occasionally, web sleuthing does turn into something tangible.

'Just knowing that somebody else cares means a great deal to the families.'- Tricia Griffith, Websleuths co-owner

On Jan. 10, thanks in part to the crowd-sourced effort to click through mostly empty swaths of snow, the plane was located. Though the passengers didn't survive the crash, the online community offered closure when a real-life search team couldn't.

The dark side of online detective work

But not all web sleuthing ends positively.

In April 2013, members of the social news website Reddit attempted to track down the Boston Marathon bombers. Users named 22-year-old Brown University student Sunil Tripathi — who had gone missing a month before the bombings— as a possible perpetrator.

Before it became clear he had nothing to do with the incident, a Facebook page set up to locate Tripathi had already been filled with accusations. The family soon suspended the page to avoid harassment. 

Griffith aims to prevent these sorts of "witch hunts" by banning the posting of personal information.

Janosch

Heriberto Janosch, based in Spain, has a personal blog devoted to solving the McCann case. He stands in front of the room rented by Madeleine McCann's family in Portugal during one of the three investigative trips to the country that he paid for out of his own pocket. (Heriberto Janosch)

"We so do not allow that. We do not allow discussion of people unless they have been mentioned or pointed out by police as a possible suspect or person of interest," she says. "The last thing we want to do is dredge up information on a person and make their life a living hell."

Despite following some cases for years, most users will never personally locate a missing person — but replacing police isn’t their goal, says Griffith.

"The last thing we want to do is interfere with the police investigation," she says, adding moderators delete posts about contacting police to avoid flooding them with redundant tips and hypotheses.

Outside the forum, however, some people go to great lengths to attempt to assist official investigations.

Heriberto Janosch has a personal blog devoted to solving the McCann case. Based in Spain, the 56-year-old has degrees in both psychology and criminology, and has paid out of his own pocket three times to travel to Praia da Luz, Portugal. Janosch says viewing satellite images can’t replace visiting the crime scene.

Through email, he describes getting a feel for the walkways and the distances between the McCann’s apartment and the bar area.

"“Also the psychosocial environment," he says. "What type of people live, work or have holidays there."

Like Chand, he read the 11,000-page case file. Janosch also went a step further and contacted both British and Portuguese police forces, recommending four people he thought should be investigated further.

Police don't always welcome amateur sleuths

But while the internet has given amateur detectives a new platform, the idea of citizens tipping off police is an old one. In fact it dates back to at least the 1800s, says criminologist Nic Groombridge.

"There’s nothing new about people trying to help police, or, indeed, naming suspects," says Groombridge, a senior sociology lecturer at St. Mary’s University in London, England.

'During the Jack the Ripper case, one of the problems the police had wasn't a lack of leads.'- Nic Groombridge, criminologist

"During the Jack the Ripper case, one of the problems the police had wasn’t a lack of leads — it was too many leads."

He says while people might have good intentions, he’s not sure police welcome the help. With the abundance of ideas they already have to go on, he says police likely don’t have time to wade through internet speculation.

Groombridge says using crowd-sourcing the examination of satellite images and CCTV footage could potentially have some use in the future, but police today aren’t overly receptive to outside help.

"Perhaps they might be better off saying what they would like people to do," he says. "I suspect they’re not yet comfortable with letting go. They’re comfortable with press conferences."