Not showing much promise as a player, he began refereeing at age 12, and was officiating adult matches in his mid-teens in Townsville.

[6] In late 2006, Shield was appointed to referee the second leg of the AFC Champions League final between Al Karama (Syria) and Jeonbuk Hyundai Motors (South Korea) was played on Wednesday 8 November at the Khaled Bin Al Waleed Stadium.

Jeonbuk Motors won the AFC Champions League after Brazilian striker Ze Carlo's 88th-minute header gave them a 3-2 aggregate victory over Al Karama.

Both were fortunate that the Australian team were knocked out in the quarter-finals because they would not have been able to referee matches involving or affecting their own country in the latter stages.

In an exhibition match won 5-3 by the home team, Shield sent off LA Galaxy defender Kevin Harmse and also booked Beckham for a retaliatory lunge at Sydney's Robbie Middleby.

Shield officiated in the quarter-final between Étoile Sportive du Sahel and Pachuca in front of 34,934 fans at the National Stadium, Tokyo.

[12] Shield left the position in September 2012 after announcing that he would not be renewing his contract after being offered a CEO role in another industry.