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Page last updated at 11:24 GMT, Tuesday, 15 April 2008 12:24 UK

How can you identify a criminal by the way they walk?

Street scene
All of these people have a distinctive walk

The Magazine answers...

A burglar has been caught because of his bow-legged walk, but how easy is it to catch a criminal by analysing their gait?

John Rigg was both lucky and unlucky when he was caught on CCTV near a house he had burgled.

Lucky because it didn't catch his face. Unlucky because the footage showed his walk, which was, to the casual observer, rather like John Wayne's.

Gait analysis is not as exact as fingerprinting or DNA but can provide confident matches to be used alongside other evidence, or to eliminate people from inquiries

Rigg's DNA was also found on an object near the burgled house, but the evidence of podiatrist Ian Linane was crucial in his conviction.

Linane used gait analysis on behalf of Lancashire police to establish that the bow-legged man in the blurry black and white CCTV footage, was the man police already suspected of the crime. He was jailed for two years.

With the ubiquity of CCTV cameras, many of which produce only very low quality pictures, the use of forensic podiatry is booming.

First used in 2000, in the UK, by Harley Street podiatrist Haydn Kelly, experts like Kelly and Linane have been called in by police officers in numerous investigations.

Distinctive conditions

Rigg was suffering, Linane quickly spotted, from some form of genuvarum, or bow-leggedness to the layman.

But there are many other distinctive conditions to look out for. The suspect might display circumduction, where they swing their leg out to the side when they are walking. Or abduction of the arm, where it moves out to the side when moving.

John Rigg
John Rigg's distinctive walk was caught on CCTV

"You could probably do a certain element of this yourself - all humans have to recognise someone by the way they move," says Linane, who treats foot and ankle problems as his day job.

But the forensic podiatrist goes further. Taking a frame by frame analysis of video of the suspect, analysing each and every element.

"Gait means the way people walk, but it's every aspect - how they use their head, their shoulders, their arms, their elbows."

The podiatrist will then advise investigators on how to get the right footage for comparison purposes with the original CCTV of the suspect to confirm identity.

Linane's analysis might include an explanation of how holding an object like a weapon is altering the gait. And wearing bulky or baggy clothes does not stop the analysis.

Victim elimination

On one occasion, he was able to identify that a round-shouldered suspect and a square-backed man in a video were one and the same by demonstrating how walking with hands in his back pockets and elbows close together was radically transforming his stance.

On another, he identified footage of someone entering and leaving an alley, with the film only showing the legs. It was possible to assert that the person entering, the victim, was not the person leaving.

A regular part of the BBC News Magazine, Who, What, Why? aims to answer some of the questions behind the headlines

The process is a "painstaking frame-by-frame assessment of movement", Linane says, and can take many days. But it has been useful as evidence in cases like Rigg's and in eliminating people from inquiries - including several murder investigations and high profile robberies.

"If you have got a crime scene where there is CCTV and there is an image of an individual, you can't see their face sometimes. There is a facial view but there might be reflected glare."

Linane concedes that gait analysis is not like fingerprinting where a 100% match can be found. But there is a sliding scale, he says, between a possible match and near definite identification.

In the movies it's even easier to see who did it.

From childhood, Linane noticed the baddies in Westerns had "externally rotated foot position" - their legs and feet were turned outwards.

"That was what baddies were meant to walk like."

Sadly, in the real world, the criminals have many different walks.


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