A dangerous play where a player comes from behind an opposing skater and trips the player unexpectedly by dragging the skate so the victim falls to the ice and quite often hits his head or lands hard due to the sneaky nature of the crime.
The slew foot is considered one of the dirtiest cheap shots a hockey player can do, particularly due to the unexpected sneaky nature of the infraction.
Match penalties can be assessed by the referee when a player delibrately takes these kinds of penalties. However, sometimes players can commit the foul by accident when skating up behind a player and attempting to body check them. Even the best players in the game get accused of slew footing - Alex Ovechkin and Sidney Crosby for example in 2009 and 2010 in separate incidents.
Although it is considered a severe penalty, there is often debate when slew footing penalties are examined for further suspension. Besides numerous small suspensions, a severe injury or suspension is rarely seen.