One of Calgary's most prolific child sex offenders says he's not a danger to the public and wants the province's top court to overturn his indefinite sentence.

Kenneth Hornby, 60, has a 30-year history of molesting young boys. Most recently, in 2018, he sexually assaulted a five-year-old boy in an alley.

Two weeks ago, Hornby was sentenced for that crime. Prosecutors Vicki Faulkner and Zailin Lakhoo successfully argued Hornby should be declared a dangerous offender and handed an indefinite sentence.

In agreeing with the Crown's position, Justice Suzanne Bensler found "no lesser measure [would] adequately protect" the public.

But this week, Hornby filed a hand-written notice of appeal, asking for the dangerous offender designation to be overturned and a five-year sentence imposed.

"I do not believe that I am a danger to the public," he wrote.

"I believe with continued treatment programs that I can curb my behaviour."

Hornby said nobody took into account his 20-year break in offending and that he has not had adequate representation from defence lawyers over the past 25 years.

Kenneth Hornby has a 30-year history of sexually abusing young boys. In 1995, he participated in a CBC documentary on the mind of a pedophile. (CBC)

In 1995, Hornby told a CBC interviewer there was no guarantee he would be able to stop himself from abusing children despite his involvement in some of the country's most intensive treatment programs.

His criminal history dates back to 1986, when he was convicted of gross indecency in Calgary for molesting two young boys, ages 13 and eight. He was sentenced to 18 months in jail.

He received the same sentence again in 1987 after convictions for sexual assault. Again, his victims were young boys.

Another sexual assault conviction came in 1992 with a 30-month sentence for molesting a 10-year-old boy.

Following his release, Hornby did not face charges again until he was caught with child pornography in 2017.

The following year, Hornby molested a five-year-old boy in a Calgary alley.

Hornby has been assessed as a high risk to reoffend.

If he responds sufficiently to treatment, he could be released, but the Parole Board of Canada would have to be satisfied that the risk to the community would be low.

A date for appeal arguments has not been set.