Vile ... Duncan McAlister

A TWISTED paedophile who trawled the web for footage of child rape and "Maddie porn" has avoided jail — because he is disabled.

Vile Duncan McAlister, 24 — who suffers from brittle bone disease — was snared with almost 500 sick images of kids on his computer.

But yesterday Ayr Sheriff Jack McGowan claimed that there was no point in caging wheelchair-bound McAlister because prison chiefs could not cope with his medical needs.

He told the fiend: "I'm conscious of your personal circumstances.

"You are not able to live independently, you can't walk or even go to the toilet on your own.

"It's highly unlikely that the prison authorities would be able to provide for you."

Ayr Sheriff Court heard McAlister admitted spending two years downloading filth from the web from 2007 to 2009. His sick searches also included "pre-teen paedo", "toddler little girl".

But prosecutors were unable to confirm if his search for "Maddie porn" was in relation to missing Madeleine McCann.

McAlister, of Ayr, was given three years' probation with psychiatric treatment, and put on the sex offenders' register for three years.

Sheriff McGowan added: "Only a community-based disposal could deal with your psychiatric problems."

Tory justice spokesman John Lamont said: "It is unacceptable that people avoid prison for any other reason than the seriousness of their crimes."

gordontait@the-sun.co.uk