Walkom was previously announced as one of the eight referees for the two conference finals, but it was unknown whether he would work the Western Conference series after making a controversial call in Game 7 of the Blackhawks-Detroit Red Wings' semifinal series.
Walkom called coincidental roughing penalties on the Blackhawks' Brandon Saad and the Red Wings' Kyle Quincey late in the third period of the Blackhawks' 2-1 overtime victory. As he was calling the play dead, Blackhawks defenseman Niklas Hjalmarsson was scoring what was thought to be the go-ahead goal.
The NHL confirmed Walkom did signal play to stop before Hjalmarsson scored, allowing the game to remain tied 1-1. Brent Seabrook won the game for the Blackhawks in overtime.
Walkom had not appeared in either conference finals series this season. He was a standby official for Game 1 of the Eastern Conference finals series between the Boston Bruins and Pittsburgh Penguins on Saturday.
Walkom is the former director of officiating who was also on the ice in Game 3 of the Blackhawks' quarterfinal series with the Phoenix Coyotes last season. Walkom and referee Ian Walsh failed to call a penalty on Coyotes forward Raffi Torres after Torres delivered a high hit on Blackhawks winger Marian Hossa. Hossa missed the rest of the series while Torres was subsequently suspended for the rest of the postseason.
Walkom was also part of the rotation of referees that officiated the 2010 Stanley Cup finals, including Game 6. The Hawks won that game over the Philadelphia Flyers in overtime but the puck from the Cup-winning goal, shot by Patrick Kane, has never been recovered. Walkom also worked the Stanley Cup finals in 2011.