Having finished 38th at the 2000 Olympic Games in Sydney, he was unable to compete at the 2004 Olympic Games in Athens following a serious road accident where he broke his back.
Fully recovered, he represented Ireland at the 2008 Olympic Games in Beijing.
In March 2009, Costin set a new Irish record of 3.50.52 at a race-walking meet in Dudince, Slovakia.
He therefore qualified to compete in 2009 World Championships in Berlin.
He is married to Zuzanna Malikova, a Slovak Olympian.