A man who pushed a snowboarder off an Aspen chairlift is expected to plead not guilty by reason of insanity to charges related to the incident.

The Aspen Times reports that 32-year-old Thomas Proesel is charged with attempted assault and reckless endangerment for pushing Seth Beckton on Jan. 17, causing him to fall about 25 feet into deep snow. The snowboarder was uninjured.

Proesel's attorney, Pamela Mackey of Denver, says she plans to have her client plead not guilty by reason of insanity in District Court via Skype or phone because he is undergoing mental health treatment in Tennessee.

Aspen prosecutor Andrea Bryan says entering such pleas requires Proesel to be present in the courtroom.

A judge will decide on the matter April 18.