On 14 July 2013, Simpson announced that she had tested positive for the drug oxilofrine. In April 2014, the Jamaica Anti-Doping Commission announced that she would be suspended for 18 months over doping charges, expiring in December that year.[2] However, after appealing to the Court of Arbitration for Sport (CAS), the suspension was lifted on 14 July 2014.
Simpson won the gold medal in the women's 200 m at the 2006 Commonwealth Games, beating Olympic champion Veronica Campbell and completing a Jamaican sweep of 100–200 m gold medals. Jamaica also won both sprint hurdles gold medals.
At the 2008 Summer Olympics in Beijing she competed at the 100 m sprint. In her first round heat she placed third behind Yevgeniya Polyakova and Jade Bailey in a time of 11.48 to advance to the second round. There she improved her time to 11.02 seconds to win her heat in front of Muna Lee and Chandra Sturrup. With 11.11 seconds in her semi final race she placed fourth and earned her spot in the Olympic final. In a remarkable race with fellow Jamaican Shelly-Ann Fraser taking the gold, Simpson and Kerron Stewart both finished in 10.98 seconds to share the silver medal and to complete the Jamaican sweep.[1] Together with Fraser, Stewart, Sheri-Ann Brooks, Aleen Bailey and Veronica Campbell-Brown she also took part in the 4 × 100 m relay. In their first round heat (without Simpson and Stewart) they placed first in front of Russia, Germany and China. Their time of 42.24 seconds was the first time overall out of sixteen participating nations. With this result they qualified for the final, in which they replaced Brooks and Bailey with Simpson and Stewart. Eventually they did not finish their race, due to a mistake in the baton exchange.[1]
Anti-doping rule violation
On 14 July 2013, Simpson informed that a urine sample she supplied after competing in the Jamaican national championships in June 2013 had tested positive for the banned stimulant oxilofrine, along with Asafa Powell.[3] On 10 April 2014, both athletes received an 18-month suspension from competing, which was set to expire in December that year.[2] However, after appealing to the Court of Arbitration for Sport (CAS), both athletes' suspensions were reduced to six months expiring in December 2014. CAS stated that: "They put forward that the offence committed was minor because it was caused by contamination of the food supplement Epiphany D1 by the banned substance oxilofrine.[4]