James Harris stole some whiskey from a Ceredigion pub in 1902

Legal historian Prof Richard Ireland has gone as far back as the middle of the 19th Century for a "rogues gallery" of the earliest criminal portraits.

"The mugshot was in contrast to the staged, carefully posed pictures from the Victorian era of people in their Sunday best," said Prof Ireland.

He gives a talk as part of Lens 2007 at the National Library on Saturday.

More than 30 mugshots will feature as a section in an exhibition, as part of a festival of Welsh documentary photography which runs at the library until 19 January.

Among the portraits is a shot of James Jones from Ceredigion who was snapped by the police in 1858 after an assault, one of the first mugshots ever taken in Wales.

The impact these photographs had on fighting crime in Victorian Britain will be discussed at Saturday's event.

Prof Ireland of Aberystwyth University said they were first used by police during the 1850s and they proved partially successful.

But the social perspective of the photos is also fascinating, argues the professor.

It's unclear how successful mugshots were because of the reliability of the crime figures from the time Prof Richard Ireland

"Images often of a ragged and disturbing underclass whose contemporaries might have wished to see forgotten, but whose contact with the law has left, paradoxically, an enduring and sometimes moving record," he said.

Prof Ireland added that before photo identification police had to reply on often unreliable, verbal descriptions of criminals.

But the expansion of the photographic technique created problems for the police, he added.

"We know that mugshots were partially successful, but as more and more pictures were taken the sheer volume of pictures created problems, and later fingerprints became the primary source of identification," Prof Ireland explained.

"It's unclear how entirely successful mugshots were because of the reliability of the crime figures from the time.

"The limitations of the technology also meant that it was easy for pictures to become blurred."