A 28-year-old Calgary man charged with luring a 13-year-old girl over the Internet has been found not guilty.

On Wednesday, a judge ruled there was reasonable doubt that Matthew Allan Armstrong knew the girl was underage.

"Here's this girl that claims she's older, she claims she's had sexual relations with other people - she's telling the accused that. She's putting naked pictures of herself online to him. It's no wonder the judge acquitted my client," says lawyer, Balfour Der.

Armstrong was charged after allegedly using an Internet chat line to lure a girl under the age of 16 for the purpose of having sex.

The court heard that part of the blame for Armstrong's actions lie in the fact that he has myotonic dystrophy. According to testimony, the disorder results in delays in behavioural development.

The not-guilty verdict has angered the teen's mother who says her daughter has been struggling with the ordeal. "She's not the same, she's not confident, she doesn't hang around with friends anymore. She's done outlandish things she would never have done before."

Armstrong will remain in jail because he still faces other charges stemming from another Internet luring investigation involving an undercover police officer. He will face those charges on November 6th.