A repeat sex offender has been declared a dangerous offender by a Calgary judge.

Justice Allan Fradsham told a courtroom on Thursday, the Crown proved Michael Nadolnick demonstrates repetitive aggressive behaviour and continues to pose a threat to the public.

Nadolnick's violent crimes date back to 1985.

He was convicted in 2008 for hijacking a truck, kidnapping an 18-year-old woman and forcing an elderly man to drive around while he sexually assaulted her.

Nadolnick also tried to escape custody in 2011 by assaulting a corrections officer and trying to steal a truck.

In a rare move, Justice Fradsham declared Nadolnick a dangerous offender twice, once for each of the two recent offences, which could affect when he is eligible for parole.

The dangerous offender status, however, means Nadolnick could remain in jail indefinitely as he will have to prove at the time of his eligibility for parole that his risk to society is manageable.

If released, he will remain on parole for life.