U.S. justice officials are again praising the "awe-inspiring" detective work of a Canadian police officer who unlocked a major child-pornography case in 2007 after identifying a regional brand of beer in the background of an illicit online photograph depicting the abuse of children.

Last week, Joseph Vieson, 43, of Annapolis, Maryland, was sentenced to 45 years in prison, to be followed by supervised release for life, for his role in producing child pornography.

It was the second conviction in the case, following that of Maryland resident Timothy Beers in May to a 36-year sentence.

"The international law enforcement effort that saved two little girls in Maryland from ongoing sexual abuse is awe-inspiring, and it has become a source of admiration and inspiration at national seminars focused on combating child exploitation," U.S. Attorney Rod J. Rosenstein said in a statement Friday.

The Toronto officer -- Det.-Const. Warren Bulmer -- was working as part of a global network of investigators, including the RCMP and Interpol, that seeks to identify and rescue the young victims of Internet child pornography.

The breakthrough in the case came in May 2007 when Bulmer gained access to illegal photos being shared electronically by members of a child-pornography ring.

"These images had been intercepted from a public area of the Internet,'' Bulmer told Canwest News Service in an interview earlier this year.

"There were clues in those images. One in particular had what at first looked like some sort of can or cup. I did some work on that image, enhanced it to the point where I could read enough of the label. And it turned out to be a beer can."

The image-enhancement software showed that one of the adults involved had been drinking Black & Tan -- a brand of beer produced by Yuengling, a 175-year-old Pennsylvania brewing company.

Bulmer did some research on the firm and discovered Yuengling's distribution area was "very tight'' -- only about 12 states in the northeastern corner of the United States.

"And there were only six where Black & Tan was even distributed,'' said Bulmer.

After an alert was issued to child pornography investigators in those states, a detective assigned to an Internet-crimes task force in Maine discerned another clue in the photograph -- an unusual, "Disney brand" pair of child's eyeglasses that could be traced to a limited number of ophthalmologists in the area.

A prosecutor and FBI agent in New York closed the loop. They tracked down a Maryland ophthalmologist who prescribed a pair of the Disney glasses to a girl he recognized as one of the victims in the photo.

Then, said Bulmer, the U.S. police "kicked down this guy's door in Maryland" and made the arrests.

Rosenstein, the U.S. attorney, hailed the efforts of Bulmer and his U.S. colleagues in his statement Friday. "Thanks to their extraordinary commitment and exceptional investigative skills, the discovery of a photograph in Canada led to an arrest here in Maryland and the rescue of two victimized children."

Sgt. Glenn Lang, supervisor of Maine State Police computer crimes unit, added the Vieson conviction and sentencing "is a great example of why Project Safe Childhood is so important and underscores the importance of agencies sharing information."